J 

810 


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SOLAR    HEAT 


SOLAR     H  EAT 


Its   Practical  Applications 


BY 


CHARLES  HENRY  POPE,  A.  M. 

\\;    » 

Author  of  "  Solar  Enginery,"  "  The 

Pioneers  of  Massachusetts,'* 

and  other  works 


BOSTON,   MASS. 
PUBLISHED  BY  CHARLES  H.  POPE 

221    Columbus  Avenue 
1903 


A 


t 

Copyright,  1903 
BY  CHARLES  H.  POPE 


Colonial 

Electrotyped  and  Printed  by  C.  H.  Slmonda  &  Co. 
Boston,  Mass.,  U.  S.  A, 


PREFACE. 

SUNLIGHT  is  a  common  word,  its  meaning 
early  and  universally  appreciated. 

Why  should  not  "  sunheat "  be  as  fully  under- 
stood, as  highly  estimated  as  its  twin?  For 
every  ray  of  illumination  which  comes  to  us  from 
the  sun  is  entwined  with  a  ray  of  caloric, 
equally  strong,  equally  beneficial.  And  as  the 
light  of  our  orb  of  day  has  obtained  admiration 
and  won  praise  for  vitalizing  and  enriching 
processes  in  nature  and  art,  why  should  not  fervid 
poetry  and  cool  ledgers  give  due  credit  ;o  the 
heat  of  the  sun  for  the  life,  health,  power,  and 
wealth  which  it  is  capable  of  conferring  to  a 
degree  but  slightly  recognized?  And  why  shall 
we  not  take  possession  of  this  opulence  promptly, 
eagerly,  masterfully? 

This  book  seeks  to  arouse  every  one  of  its 
readers,  especially  the  young  and  progressive, 
to  take  part  in  and  help  forward  a  world-wide 
movement  in  the  appropriation  of  the  vast  treas- 
ures which  sunheat  offers. 


258161 


CONTENTS 


PAGE 

INTRODUCTION :  Man's  ability  to  accomplish  much  by 
simple  manual  labor ;  his  reaching  out  to  procure  aux- 
iliary forces,  as  domestic  animals,  the  wind,  flowing 
water,  heat,  steam,  galvanism,  magnetism,  electricity; 
the  great  waste  of  fuel  going  on  and  the  need  of  other 
auxiliaries  ;  personal  experiences  of  the  writer  which  led 
to  the  present  treatise ;  experiments,  caveat,  pamphlet  .  9 

SOME  HISTORY  OF  SPECIAL  UTILIZATIONS 
OF  SOLAR  HEAT:  The  work  of  Archimedes, 
De  Tralles,  Bacon,  Hoesen,  De  Caus,  Buffon,  De  Saus- 
sure,  Belidor,  Poncon,  Mclvor,  Colborne,  St.  George, 
Mouchot  (notice  of  his  inventions  and  writings,  see  also 
Appendix),  Hittell,  Deitzler,  The  Solar  Heat  Power 
Company  of  California,  Mauzey,  Molera,  Cebrian,  Cal- 
ver,  Ericsson,  Adams,  Pifre  (Printing  by  Solar  Heat 
Power),  the  Auteuil  method  of  raising  water  by  solar 
heat,  the  Pasadena,  Cal.,  pumping  engine  .  .  .25 

SOME    TECHNICAL    STUDY   OF   THE   SUBJECT: 

Nomenclature ;  premises  ;  Reception  of  solar  heat ;  lo- 
cating the  meridian,  value  of  glass  covering ;  Reflection 
of  solar  heat ;  form,  material  and  arrangement  of  mir- 


viii  CONTENTS 

PAGB 

rors;  Refraction  of  solar  heat;  various  shapes  and 
cutting  of  lenses ;  lighthouse  lanterns ;  call  for  pro- 
gressive methods  in  lens-manufacture  to  meet  this 
want ;  Electric  Storage  of  Solar  Heat  Power ;  Applica- 
tions of  Solar  Heat 89 

LOCALITIES  PECULIARLY  ADAPTED  TO  THE 
UTILIZATION  OF  SOLAR  HEAT:  The  "West- 
ern Highland  "  region  of  the  United  States  of  America 
(tables  of  sunshine) ;  Algeria,  Egypt,  India,  The  Soudan, 
South  America,  Australia,  etc.;  call  for  government 
aid  in  the  development  of  the  enterprise  .  .  .130 

GENERAL  DISCUSSION  OF  THE  SUBJECT:  Why 
has  so  little  been  done  hitherto  ?  some  "  captain  of 
industry  "  may  do  a  great  work ;  the  Costless  Engine ; 
proportion  of  time  available ;  solar  heat  always  enrich- 
ing, never  impoverishing ;  subject  ought  to  interest  the 
noblest  minds 142 

APPENDIX :  Review  of  La  Chaleur  Solaire,  Ses  Applica- 
tions Industriclles,  with  its  table  of  contents  .  .  155 


INTRODUCTION. 

MAN,  relying  only  upon  his  own  strength,  the 
exercise  of  human  muscular  force,  can  accom- 
plish very  much.  He  may  fell  trees,  rive  their 
trunks  into  timbers,  boards,  shingles,  pins,  and 
tools,  and  put  these  together,  making  for  him- 
self a  commodious  and  convenient  dwelling. 
With  one  of  the  bits  of  stone  or  metal  that  Na- 
ture has  strewn  upon  the  surface  of  the  ground, 
he  may  chip  off  other  chips,  and  bring  to  an  edge 
tools  for  his  use  in  cutting  wood,  stone,  and 
metals.  Learning  by  experiment  what  can  be 
done  with  the  wedge,  the  lever,  and  the  roller, 
he  can  move  great  masses  and  build  structures 
of  immense  size.  Braiding  the  fibres  of  plants 
into  ropes,  he  can  draw  and  lift  weighty  arti- 
cles; twisting  them  into  yarns  and  cords,  he 
can  then  weave  them  into  cloths  for  a  great  va- 

9 


io  INTRODUCTION 

riety  of  uses,  to  protect  and  ornament  the  body 
and  perfect  the  convenience  and  comfort  of  his 
dwelling.  On  instruments  made  entirely  by 
hand  wonderful  melodies  and  harmonies  have 
been  produced;  on  hand-smoothed  wood  and 
hand-woven  cloth  poems  and  histories  have  been 
written,  mathematical  problems  calculated,  and 
artistic  conceptions  wrought.  Making  use  of  the 
vital  energy  which  he  finds  operating  in  plants 
and  animals,  he  tills  the  soil  and  raises  stock, 
till  farm  and  garden  and  flock  and  herd  reward 
his  toil. 

Having  discovered  fire  (first  becoming  ac- 
quainted with  it,  perhaps,  as  a  product  of  light- 
ning), experiment  shows  him  the  value  of  heat 
to  improve  the  quality  of  fruit  and  flesh  and  to 
bring  metals  into  plastic  condition.  Then,  still 
making  use  of  human  power  alone,  he  has  gone 
on  enlarging  the  sphere  of  his  activities,  the 
wealth  of  his  achievements. 

But  at  a  period  very  remote,  man  learned  to 
domesticate  animals,  and  add  their  force  to  his 
own.  He  bade  them  draw  his  plow,  tread  out 
his  grain,  move  his  heavy  loads,  and  bear  his 


INTRODUCTION  n 

burdens.  Next,  he  turned  to  the  wind,  which 
often  hindered  his  movements,  and  tamed  it  to 
be  his  servant.  Stretching  with  his  own  hands 
the  fans  and  sails  of  his  mill,  he  calmly  awaited 
the  approach  of  the  gale,  and  laughed  as  the 
attacking  party  became  his  servant.  He  spread 
the  cloth  his  hands  had  woven  on  the  spars  his 
fingers  had  shaped,  and  the  conquered  wind  be- 
came his  galley-slave.  The  torrent  rushing  down 
the  hillside  was  caught  by  his  nimble  fingers,  and 
made  to  do  his  bidding,  turning  his  water-wheel. 
By  and  by  a  compound  force  was  invented, — 
Steam,  —  child  of  the  father  Fire  and  the  mother 
Water,  a  very  Samson.  Now  the  progress  of 
man's  achievements  became,  shall  we  say,  a  thou- 
sandfold greater  than  before?  Surely  man,  with 
the  auxiliary  steam,  has  been  writing  history 
at  a  prodigious  rate  compared  with  his  former 
movements. 

One  more  tremendous  force  has  been  brought 
into  man's  possession  and  use,  —  rather  a  triad 
of  forces,  Magnetism,  Galvanism,  and  Electric- 
ity. The  first  was  domesticated  by  the  almond- 
eyed  citizens  of  the  Central  Flowery  Kingdom 


iz  INTRODUCTION 

many  centuries  ago  in  the  mariner's  compass; 
the  other  two  coquetted  with  philosophers  for  a 
long  period ;  but  the  trio  to-day  are  saddled  and 
harnessed  for  the  every-day  service  of  the  rich 
and  poor  alike  in  a  multitude  of  ways. 

What  more  do  we  need?  Have  we  not  forces 
and  machinery  sufficient  for  all  present  and  pro- 
spective uses?  We  are  still  improving  all  the 
auxiliaries  which  we  have  adapted  to  our  use; 
still  learning  the  laws  of  heat;  still  improving 
the  breeds  of  our  domestic  animals;  still  inves- 
tigating agricultural  processes;  making  innu- 
merable improvements  in  steam  and  electrical 
enginery,  and  so  on. 

MAN   IS   CRIPPLED   FOR   LACK   OF   AUXILIARIES. 

But  meantime,  the  opportunities  and  demands 
of  human  activity  have  increased  far  more  rap- 
idly than  the  exercise  of  human  power,  or  the 
application  of  known  principles,  or  the  appropri- 
ation of  external  forces;  and  man  is  crippled 
to-day  for  lack  of  auxiliaries.  It  costs  too  much 
to  raise  many  of  the  articles  which  are  needful 


INTRODUCTION  13 

for  the  support  of  life ;  it  costs  too  much  to  make 
many  of  the  things  which  have  come  to  be  rec- 
ognized as  essential  to  a  complete  existence  and 
happiness;  and  an  immense  sphere  for  discovery 
and  appropriation  still  awaits  us  after  all  the 
years  of  man's  residence  on  this  planet.  We 
must  have  more  of  the  sort  of  help  that  the  wind 
gives;  more  of  such  aid  as  steam  furnishes; 
more  of  the  service  now  rendered  us  by  flowing 
streams  and  burning  liquids  and  gases.  Some 
other  Titan  must  be  found  to  bear  our  loads, 
till  our  fields,  warm  our  dwellings,  develop  our 
mines,  and  extend  the  sway  of  our  race  over  the 
irrational  and  inanimate. 

One  large  motive  to  this  search  for,  and  appro- 
priation of,  a  new  auxiliary  is  the  frightful  de- 
struction of  material  which  is  carried  on  by  our 
fuel  systems.  Forests  are  being  swept  away  from 
hills  and  valleys;  coal  is  being  drawn  up  from 
miles  and  miles  of  mines.  The  year  1902  has 
added  an  awful  chapter  to  the  history  of  our  need 
of  a  new  source  of  heat  and  power,  by  the  wide 
suffering  and  impoverishment  of  the  people  of 
the  eastern  United  States,  in  consequence  of  the 


14  INTRODUCTION . 

Pennsylvania  coal  strikes.  Can  we  not  discover 
or  use,  if  already  discovered,  something  which 
will  be  obtainable  without  the  consent  of  either 
"  operators  "  or  "  organized  laborers  ?  "  Can 
we  not  employ  something  which  will  still  remain 
for  to-morrow  after  we  have  used  it  to-day?  As 
the  flowing  stream  gives  its  aid,  so  may  not  other 
natural  movements  be  harnessed  into  our  ser- 
vice? And  is  there  not  something  more  stable 
than  the  river  current,  which  depends  for  its 
fulness  on  rainfall  and  other  conditions? 

PERSONAL   EXPERIENCES   OF   THE    WRITER. 

This  quest  has  long  interested  the  writer.  Be- 
coming a  resident  of  California  in  1865,  he  saw 
much  of  the  country  from  North  to  South.  In 
the  year  1875,  living  in  Oakland,  he  began  a 
series  of  experiments  in  the  investigation  of 

SOLAR    HEAT. 

He  used  lenses  first,  "  burning  glasses,"  read- 
ing-glasses, photographic  lenses,  etc.  It  was 


INTRODUCTION  15 

interesting  to  watch  the  varying  operation  of 
lenses  of  different  size.  A  pocket  magnify  ing- 
glass,  one  inch  and  an  eighth  in  diameter,  would 
concentrate  heat  enough  to  set  paper  on  fire  in 
a  tiny  spot  in  a  second  or  more.  The  larger  the 
lens,  the  broader  the  spot  or  section,  which  would 
flame  up  and  burn  out  the  paper  in  the  same  time. 
A  glass  three  inches  wide  would  set  wood  afire; 
one  six  inches  across  would  bore  a  hole  through 
a  shingle;  one  of  eight  inches  diameter  would 
burn  very  hard  wood,  and  inflame  a  disc  the 
size  of  a  dollar  on  the  paper.  Then  the  investi- 
gator turned  his  attention  to  reflectors.  He  saw 
the  light  streaming  out  in  front  of  a  locomotive 
from  the  silvered  headlight  reflector;  there  the 
rays  of  a  lamp  were  sent  against  the  inner  walls 
of  the  reflector  and  then  turned  away  in  parallel 
lines  along  the  track.  The  old  maxim  came  to 
his  mind :  "  What  will  fetch  will  carry ;  "  the 
rays  of  the  sun,  falling  in  parallel  lines  on  the 
inner  surface  of  the  reflector,  will  be  reflected 
to  the  focus  where  now  the  lamp  is  placed.  And 
the  heat  of  the  sun  can  be  concentrated  as  well 
as  its  light,  since  both  are  under  the  same  laws 


16  INTRODUCTION 

of  undulation.  Impressed  with  this  idea,  he  bor- 
rowed of  the  master  mechanic  at  the  railroad 
shop  a  spare  headlight  reflector;  took  it  to  his 
residence;  set  it  up  in  a  simply  constructed 
framework,  and  inserted  at  the  focus,  where  the 
lamp  had  been,  a  tube  of  galvanized  iron,  black- 
ened. Turning  the  frame  toward  the  sun,  so 
that  the  rays  fell  directly  into  it,  he  waited  five 
minutes  only,  when  the  quart  of  water  he  had 
poured  into  the  tube  began  to  boil;  later  he 
cooked  eggs  in  the  water,  and  did  other  culinary 
performances  not  needful  to  detail.  Placing 
pieces  of  wood  at  the  focus,  he  found  them 
quickly  burned ;  antimony  glance,  a  metal  of  low 
melting  point,  soon  flowed  at  the  focus,  and  some 
other  metallic  compounds  yielded  also. 

If  the  parson  had  been  a  mechanical  man,  able 
to  construct  apparatus,  or,  if  he  had  possessed 
spare  cash  for  the  employment  of  skilled  helpers, 
there  might  have  been  some  valuable  progress 
made.  Unable  to  pursue  the  investigations  far- 
ther at  that  time,  he  contented  himself  with  fil- 
ing, through  the  patent  agency  of  The  Scientific 
Press,  of  San  Francisco,  a  caveat  for  an  inven- 


INTRODUCTION  17 

tion  of  a  transmitter  of  heat  obtained  from  con- 
centrated solar  rays. 

EXTRACTS  FROM  THE  CAVEAT. 

The  Theory. 

ist.  That  the  rays  of  the  sun  fall  in  parallel 
lines,  and  may  be  focalized  in  a  point  by  refrac- 
tion on  one  side  of  a  given  plane,  or,  by  reflection, 
meeting  like  the  radii  of  a  sphere  at  its  centre, 
from  every  side  except  that  exposed  to  direct 
rays. 

2d.  That  the  parabolic  mirror  is  the  best  form 
of  reflector,  and  that  its  surface  may  either  be 
polished  or  glistening  white,  e.  g.  "  hard  finish ;  " 
the  latter  by  far  the  least  expensive. 

3d.  That  machinery  of  the  simplest  sort  will 
give  to  such  a  mirror  a  motion  which  will  keep 
its  face  toward  the  sun,  even  if  its  size  be  ex- 
ceedingly large. 

4th.  That  the  degree  and  amount  of  heat  at 
the  focus  will  be  proportionate  to  the  area  of  the 
opening  of  the  lens  or  mirror ;  and  that,  thus,  the 
only  limit  to  the  temperature  which  may  be 


i8  INTRODUCTION 

reached  is  the  size  to  which  such  lenses  and 
mirrors  may  be  constructed  and  revolved. 

5th.  That  the  temperature  of  the  air  through 
which  rays  pass  immediately  before  focalization 
affects  the  focal  temperature.  From  which  it 
would  follow  that  the  hot,  rainless  districts  of 
the  Sierra  Nevada  et  ah.  will  afford  a  very  high 
degree  of  heat,  and  that  there  would  be  some 
accumulation  of  heat  in  some  proportion  to  the 
time  of  exposure  of  surface. 

6th.  That  any  substance  may  (practically)  be 
heated  at  or  near  the  focus  which  does  not  in- 
jure the  surface  of  the  reflector  by  steam,  smoke, 
or  decrepitation;  and  any  substance  may  be  re- 
torted there. 

7th.  That  the  best  form  of  retort  is  spherical 
or  spheroid,  with  conical  apertures  pointing 
toward  the  centre;  which  would  multiply  the 
heating  surface  like  boiler  tubes.  The  delivery 
pipe  from  this  retort  to  be  passed  (i)  directly 
back  through  the  shaded  portion  of  the  reflector, 
or  (2)  forward  and  down  through  a  slit  in  the 
reflector  on  to  a  rotating  table.  For  melting 


INTRODUCTION  19 

ores,  the  first  may  admit  the  ore,  the  latter  con- 
duct out  the  liquid. 

The  claim  was  then  given : 

"A  is  a  parabolic  mirror,  which  is  mounted 
upon  a  suitable  frame,  and  with  the  proper  solar 
mechanism  for  rotating  it,  with  its  face  con- 
stantly to  the  sun." 

The  device  for  which  the  inventor  particularly 
sought  protection  was  described  as  "  An  opaque, 
globular  retort,  B,  provided  with  numerous  con- 
ical spaces  which  extend  radially  toward  the 
centre,  and  serve  to  carry  the  heat  throughout 
the  interior  space,  from  which  it  is  conveyed  by 
a  tube,  C,  through  the  rear  of  the  mirror  to  the 
distributor,  D.  The  discharger  may  consist  of 
numerous  conical  spaces,  E,  which  project  radi- 
ally in  every  direction  from  the  central  globe,  D, 
into  the  medium  to  be  heated,  and  by  this  or 
some  equivalent  device  I  am  enabled  to  utilize 
the  heat  of  the  sun  for  many  purposes.  The  con- 
centrating and  diffusing  devices  are  especially 
useful  for  many  other  purposes,  and  I  desire  to 
especially  protect  myself  in  the  use  of  these 
parts,"  etc. 


20  INTRODUCTION 

This,  the  writer  believes,  was  the  first  appli- 
cation at  the  United  States  Patent  Office  for  any- 
thing relating  to  solar  heat. 

It  may  be  of  small  value;  but  the  point  was 
made  as  a  beginning  of  inventions  for  which 
he  hoped  to  get  time  later  on.  He  made  the 
matter  no  secret;  talked  with  many  friends  and 
acquaintances  of  it.  One  friend  was  a  reader  of 
the  Scientific  American,  and  called  the  writer's 
attention  to  the  article  which  appeared  in  that 
journal,  touching  the  French  discoveries  and 
constructions  in  the  matter,  of  which  he  had  been 
utterly  ignorant  before.  From  that  time  he  re- 
garded himself  as  a  pledged  student  of  the  sub- 
ject, and  read  what  he  could  find,  and  find  time 
for. 

The  date  of  the  application  for  the  caveat 
above  mentioned  was  April  10,  1875;  the  date 
of  the  Scientific  American's  article  on  the  French 
invention  was  September  13,  1875.  The  writer 
allowed  the  matter  to  pass  until  after  he  had 
removed  to  the  Atlantic  coast  again.  March 
22,  1883,  residing  at  Farmington,  Maine,  he 
contributed  to  the  Lewiston  Evening  Journal 


INTRODUCTION  21 

(known  as  "Congressman  Dingley's  paper") 
an  article,  in  which  he  gave  some  history  of  the 
development  of  the  applications  of  solar  heat; 
and  this  paper  was  reprinted  from  the  Journal, 
and  issued  in  pamphlet  form  under  the  title, 
"  Solar  Enginery."  Copies  of  the  pamphlet  were 
placed  in  a  number  of  the  leading  libraries  of  the 
world,  and.  sent  to  some  persons  notable  in  science 
or  prominent  in  government;  responses  came 
back  from  a  good  number  of  them;  and  the 
writer  had  much  pleasure  in  finding  that  he  had 
opened  a  new  field  of  thought  and  investigation 
to  quite  a  large  number  of  persons.  Certain 
errors  in  his  historical  statements  were  kindly 
pointed  out,  and  proffers  of  assistance  and  coop- 
eration made  by  some.  But  a  very  busy  life  hin- 
dered him  from  contributing  anything  of  impor- 
tance to  the  study.  He  spent  some  money  and 
time  in  experiments  in  certain  classes  of  appa- 
ratus, but  without  marked  success.  Some  of  his 
correspondents  were  aided  by  him  and  did  better. 
He  has  seen  some  progress  made  in  public 
interest  in  the  subject;  carping  criticism  and 


22  INTRODUCTION 

scorn  have  passed  pretty  much  away ;  every  time 
he  has  given  "  talks  "  on  the  matter,  he  has  been 
rewarded  by  active  questioning  and  by  positive 
respect  shown  the  topic  and  his  statements. 
Meantime  the  enterprise  of  California  and  Mas- 
sachusetts has,  as  public  fame  declares,  brought 
things  to  a  practical  success  in  certain  cases ;  the 
demonstration  is  complete  along  some  lines ;  and 
there  ought  to  be  from  this  very  point  definite 
progress  along  the  whole  front.  There  is  a  hesi- 
tation, however,  a  failure  to  advance  rapidly. 
The  writer  believes  that 

SOME  CALL  TO  THE  PEOPLE 

is  needed;  some  information  on  the  subject  fur- 
nished in  a  manner  to  arouse  interest  and  make 
a  demand  for  the  ovens,  furnaces,  engines,  which 
it  is  possible  now  for  manufacturers  to  produce. 
It  is  also  necessary  that  some  stir  come  to  invent- 
ors, to  ingenious  men,  handy  men,  to  anybody 
who  can  find  out  new  ways  of  "  catching  the 
sunbeams  "  and  extracting  gold  from  them. 


INTRODUCTION  23 

THE    PURPOSE   OF   THIS    BOOK. 

Therefore  he  comes  before  the  public  in  the 
present  treatise,  in  which  he  endeavors  to  trace 
the  history  of  attempts  and  successes  in  the  utili- 
zation of  solar  heat;  examine  a  portion  of  the 
laws  and  limitations  of  the  subject;  discuss  ways 
and  means;  and  attempt  to  arouse  his  readers 
to  give  to  the  matter  their  energy  and  invention, 
their  brain  and  capital;  that  we  may  very  soon 
see  solar  enginery  take  its  place  by  the  side  of 
steam  enginery  and  electrical  enginery  and  gas 
enginery  in  the  public  estimation,  in  technical 
schools,  in  mechanical  journals,  and  in  myriads 
of  practical,  labor-saving  constructions. 


SOLAR     HEAT 

Its  Practical  Applications 


CHAPTER   I. 

SOME    HISTORY   OF   SPECIAL   UTILIZATIONS   OF 
SOLAR    HEAT. 

THE  earliest  instance  on  record  of  the  practical 
application  of  solar  heat  to  aid  man  in  his  under- 
takings is  the  alleged  attack  of  a  Syracusan 
scholar  upon  the  Roman  fleet  in  the  year 
214  B.  c.  with  burning  mirrors. 

Syracuse  was  the  largest  city  of  ancient  Sicily. 
Long  independent,  many  years  an  ally  of  Rome 
while  its  intelligent  king,  Hiero,  lived,  it  had 
been  estranged  from  the  Italian  government  by 
his  grandson  and  successor,  Hieronymus,  and 

25 


26  SOLAR   HEAT 

had  allied  its  fortunes  to  those  of  Carthage. 
Marcellus,  the  Roman  ruler,  came  down  upon 
the  city  with  his  imposing  force  of  ships,  and 
the  struggle  was  severe.  Archimedes,  the  most 
renowned  mechanician  of  the  age,  discoverer  of 
the  ratio  between  the  circumference  and  diameter, 
and  of  the  law  of  specific  gravity,  who  had  been 
a  pupil  of  Euclid  in  Alexandria,  set  himself 
to  work  to  aid  his  native  land.  He  bethought 
himself  of  the  mighty  power  of  the  sun.  So 
he  caused,  as  is  supposed,  a  number  of  brazen 
plates  to  be  constructed;  had  their  surfaces  pol- 
ished to  the  highest  degree  possible,  and  then 
arranged  them  along  the  shore  in  some  way  not 
clearly  described,  so  that  the  reflected  rays  were 
concentrated  upon  the  hulls  and  rigging  of  the 
Roman  ships  which  lay  in  the  harbor  or  sailed 
near  the  shore,  setting  some  of  them  on  fire,  and 
striking  terror  into  the  hearts  of  the  sailors  to 
such  an  extent  that  the  fleet  was  temporarily 
scattered,  and  the  city  rid  of  their  presence  for 
a  brief  period.  The  siege  was  renewed  after  a 
little,  to  be  sure;  the  inventor  was  struck  down 
by  the  sword  of  a  Roman  soldier;  and  Syracuse 


ITS   PRACTICAL   APPLICATIONS        27 

became  a  Roman  province.  But  the  philosopher's 
use  of  the  sun's  heat  had  taken  its  place  upon 
the  world's  arena,  and  was  entered  in  the  world's 
records.  *  Later  historians  made  something  of  it ; 

1Anthemius  de  Tralles,  a  celebrated  architect,  whose 
chief  monument  is  the  superb  basilica  of  Ste.  Sophia  in 
Constantinople,  dying  in  the  year  584  A.  D.,  left  among 
his  writings  four  treatises  upon  burning  mirrors,  fragments 
of  which  are  still  extant.  The  second  of  these  is  on  the 
problem,  "  How  to  construct  a  machine  capable  of  setting 
an  object  on  fire  at  a  distance  by  means  of  solar  rays." 

Roger  Bacon,  an  English  monk,  advocated  the  use  of 
burning  mirrors  about  the  year  1280  A.  D.,  and  actually 
constructed  and  offered  for  sale  at  £10  apiece  some  excel- 
lent ones  of  steel.  But  his  genius  and  progressiveness  made 
him  enemies,  and  brought  him  obloquy  and  long  imprison- 
ment. He  died  in  the  year  1294. 

Mirrors  were  manufactured  in  Dresden,  about  1755,  by 
a  mechanic  named  Hoesen,  of  parabolic  form,  nine  feet 
and  a  half  in  diameter,  constructed  with  wooden  frames, 
having  thin  plates  of  brass  for  a  reflecting  surface  within. 
With  these  he  and  his  patrons  experimented  in  setting  fire 
to  objects  at  various  distances;  but  we  have  no  record 
of  their  applying  them  to  the  needs  of  the  home  or  the 
factory. 

Salamon  de  Caus  (1576 — 1626),  a  French  engineer,  in- 
vented and  described  in  1615  the  first  machine  for  raising 
water  by  means  of  the  heat  of  the  sun.  Another  French 
engineer,  Bernard  Foret  de  Belidor  (1697—1761),  gives  an 
excellent  account  of  this  "continual  fountain,"  as  its 
designer  termed  it 


SOLAR   HEAT 


[)• I 


THE    CONTINUAL   FOUNTAIN   OF   SALAMON 
DE  CAUS  (l6l5). 


ITS   PRACTICAL   APPLICATIONS         29 

but  it  would  seem  that  the  event  was  looked 
upon  as  a  freak,  a  piece  of  magic,  an  eccentricity ; 
no  successor  of  the  great  Archimedes  arose  for 
centuries  to  carry  out  his  incomplete  designs,  or 
produce  in  full  what  he  had  performed  in  em- 
bryo. In  fact,  the  time  came  when  many  stu- 
dents of  history  scoffed  at  the  record  of  the 
burning  of  the  fleet,  and  called  the  story  a  fable, 
a  canard. 

But  there  arose  a  man,  after  nineteen  centuries 
had  gone,  who  determined  to  test  the  practicabil- 
ity of  the  alleged  performance  of  Archimedes. 
The  French  naturalist  and  philosopher,  Buffon, 
about  the  year  1747,  made  a  series  of  experi- 

After  filling  the  dome,  A  B  N  C,  to  the  line  B  C,  the 
heat  of  the  sun  on  the  dome  so  expands  the  air  in  its 
upper  portion  that  the  pressure  drives  part  of  the  water 
(which  cannot  go  down  on  account  of  the  valve  at  K)  up 
through  the  valve  F  into  the  reservoir  H.  When  (at  night, 
for  example)  the  globe  is  cooled  and  the  air  in  it  ex- 
panded, water  will  rise  from  below  through  the  valve  K 
and  the  tube  K  N,  until  the  air  in  the  globe  is  condensed 
to  the  same  degree  as  the  outer  air  which  presses  upon  the 
surface,  M  I,  of  the  water  below.  This  cycle  will  be 
repeated  every  day  and  night  when  the  one  is  sufficiently 
warm  and  the  other  sufficiently  cool.  Of  course  artificial 
cooling  might  be  applied  and  frequent  cycles  secured- 
[Mouchot.] 


30  SOLAR   HEAT 

ments  which  demonstrated  completely  the  entire 
practicability  of  the  performance  attributed  to 
the  Syracusan  in  the  third  century  before  Christ. 

M.  Buffon  caused  a  large  framework  to  be 
built,  on  which  he  hung  pieces  of  silvered  glass, 
whose  reflections  were  all  turned  on  one  point. 
Then  he  varied  the  number  of  pieces  and  the  dis- 
tances of  objects,  which  he  subjected  to  the  focal- 
ized heat  of  the  sun,  and  tabulated  the  results. 

With  17  mirrors,  at  20  feet,  he  heated  thin 
pieces  of  iron  to  redness. 

With  45  mirrors,  at  20  feet,  he  melted  a  pew- 
ter flask  of  six  pounds'  weight. 

With  128  mirrors,  at  150  feet,  he  burned  a 
tarred  plank. 

With  154  mirrors,  at  150  feet,  he  made  a 
tarred  plank  smoke  in  two  minutes  when  the 
sky  was  obscured. 

With  154  mirrors,  at  250  feet,  he  burned 
chips  of  wood  covered  with  charcoal  and  sulphur. 

All  this  was  done  in  France,  where  the  tem- 
perature of  solar  rays  could  not  have  been  as 
high  as  at  Syracuse,  making  a  perfect  proof  of 
the  historical  probability  of  the  story  told  by  the 


ITS   PRACTICAL   APPLICATIONS         31 

old  historians  concerning  the  Syracuse  ship- 
burning. 

M.  Buffon  afterward  had  a  burning  mirror, 
of  parabolic  form,  constructed,  having  a  diameter 
of  forty-six  inches,  and  performed  many  experi- 
ments with  wonderful  results.  He  does  not  ap- 
pear to  have  looked  on  the  sun  as  a  tamable 
force  for  man's  daily  use,  an  ally  for  human 
enterprise;  and  all  his  experiments  were  classed 
by  the  annalists  of  the  period  as  play,  or,  at  the 
highest,  scientific  curiosities. 

De  Saussure,  a  Swiss  philosopher  (174099), 
in  letters  to  Buffon  and  to  La  Journal  de  Paris 
described  a  set  of  concentric  glass  chambers  which 
he  had  constructed,  and  in  the  interior  of  which 
he  had  cooked  soup.  About  the  same  time  a 
French  physicist,  Ducarla,  constructed  a  some- 
what similar  apparatus  and  performed  much  the 
same  work  with  it.  [Mouchot] 

In  1764,  B.  F.  Belidor  published,  at  Amster- 
dam, the  results  of  certain  investigations  of  his 
own;  but  the  world  received  no  impulse  toward 
the  appropriation  of  the  energy  of  sunbeams  for 
real  service.  Even  Sir  John  Herschel,  when  at 


32  SOLAR   HEAT 

the  Cape  of  Good  Hope,  in  1838,  he  was  im- 
pressed with  the  tremendous  power  of  the  sun, 
failed  to  arouse  anything  of  a  practical  spirit  in 
the  British  mind. 

For  further  accounts  of  ancient  studies  and  con- 
structions, see  extracts  from  Mouchot  in  the 
Appendix. 

Antoine  Poncon,  in  1854,  obtained  a  patent  in 
London,  the  first  of  which  I  have  found  any  rec- 
ord, for  an  invention  to  utilize  solar  heat. 

"  My  invention,"  says  the  patentee,  "  consists 
in  using  the  sun's  rays  to  create  a  vacuum  in  a 
suitable  vessel,  elevated  at  the  height  of  a  column 
of  water,  which,  in  the  above  vacuum,  is  kept 
in  equilibrium  by  the  pressure  of  the  atmosphere. 
Such  vacuum  being  formed,  I  fill  it  with  water 
acted  upon  by  the  external  pressure  of  the  atmos- 
phere, and  thus  obtain  a  head  of  water  which 
may  be  applied  as  a  motive  power."  Nothing 
more  can  be  learned  of  this  invention.  Whether 
M.  Poncon  actually  constructed  a  machine  and 
produced  a  vacuum  after  this  sort,  and  did  ob- 
tain a  head  of  water  which  he  really  used  as  a 


ITS    PRACTICAL   APPLICATIONS         33 

motive  power,  or  whether  he  obtained  a  patent 
for  an  idea  (as  many  an  inventor  has  vainly  tried 
to  do  under  our  American  laws),  no  man  informs 
us. 

In  1865,  William  Graham  Mclvor,  superin- 
tendent of  the  Government  Botanical  Garden 
and  Cinchona  Plantation  in  the  Presidency  of 
Madras,  India,  obtained  a  patent  in  England, 
also,  and  Colborne  and  St.  George  a  little  later; 
but  there  comes  to  the  reader  a  strong  suspicion 
that  the  Patent  Office  admitted  essayists,  rather 
than  inventors,  to  their  lists;  and  that  these 
men  were  not  actual  makers  of  machines  which 
did  what  they  claimed.  Especially  is  this  true 
of  Mclvor,  who  tells  us,  "  on  the  average  we 
have  280  bright  days  in  a  year,  when  the  uncon- 
centrated  heat  of  the  sun  is  all  the  way  from  120 
to  1 60  Fahrenheit."  But  he  does  not  explain 
anything  he  had  done  to  utilize  it. 

While  these  studies  and  declarations  were  going 
on  in  Great  Britain,  and  nothing  more  tangible 
is  recorded,  there  was  a  definite  advance  made 
in  France,  the  home  of  Buffon,  above  mentioned. 


34  SOLAR   HEAT 

AUGUST   MOUCHOT, 

a  professor  in  the  Lycee  d'Alengon,  at  Tours,  in 
the  southern  part  of  France,  pursuing  studies 
in  mathematics,  the  department  in  which  he  was 
an  instructor,  achieved  some  very  practical  re- 
sults. He  made  a  reflector  of  a  general  parabolic 
form,  like  the  headlight  reflector  of  the  locomo- 
tive (see  Introduction),  and  placed  at  the  focus 
a  boiler  filled  with  water,  covering  it  with  a  bell- 
glass  ;  he  connected  the  boiler  with  a  small  steam- 
engine,  which  was  run  by  the  heat  of  the  sun 
alone.  This  "  insolator  "  was  a  success  to  some 
extent;  he  seems  to  have  actually  had  it  in 
operation  as  early  as  the  year  1860.  At  about 
the  same  time  he  invented  ovens,  "  les  mar- 
mites  solaires"  in  which  he  cooked  food  to  a 
certain  amount.  He  exhibited  a  solar  pumping- 
engine  in  Paris  in  1866.  [Revue  des  Deux 
Mondes,  1876.] 

The  government  became  interested  in  his 
work,  and  aided  him;  employed  him,  in  fact,  to 
construct  a  number  of  pumping-engines  for  use 
in  their  province  of  Algeria,  on  the  desert. 


ITS   PRACTICAL  APPLICATIONS        35 

These  were  not  made,  perhaps,  before  the'  ex- 
hibition, in  1875,  of  his  perfected  reflector  and 
engine,  but  some  of  them  were  in  operation  in 
1878.  He  exhibited  at  Tours,  and  afterward  at 
the  Paris  Exposition  in  1878,  a  reflector  112.3 
inches  wide,  39.3  inches  at  base,  with  an  engine 
at  the  focus,  which  pumped  water  very  rapidly 
and  worked  successfully.  He  obtained  patents 
for  various  forms  and  parts  of  his  inventions  in 
France,  and  also  in  England. 

All  must  unite  in  honoring  him  as  the  greatest 
of  the  pioneers  in  solar  enginery.  The  world 
owes  him  a  large  debt. 

POSTSCRIPT. 

After  the  present  work  had  gone  to  press  the 
writer,  being  in  London,  saw  for  the  first  time 
M.  Mouchot's  book,  "La  Chaleur  Solaire,  Ses 
Applications  Indwtrielles"  in  the  library  of  the 
British  Museum.  He  immediately  ordered  a  copy 
and  read  it,  with  keen  interest  and  admiration. 
From  its  pages  he  made,  on  his  return  to  America, 
a  few  extracts  which  he  incorporated  in  the  final 


36  SOLAR   HEAT 

proof-reading  of  this  volume,  giving  credit  for 
the  same  in  every  case;  he  also  added  in  an 
appendix  a  translation  of  the  title  and  contents  of 
M.  Mouchot's  work,  in  order  that  his  readers 
might  get  something  of  the  benefit  which  the 
professor's  pages  afford. 

M.  Mouchot  began  to  give  his  attention  to  the 
study  of  solar  heat  in  1860.  He  received  a  patent 
from  the  French  government  in  1861.  In  1864 
and  1865  he  made  valuable  inventions  in  pumping 
apparatus  based  on  the  "  continual  fountain " 
of  De  Caus,  and  exhibited  also  parabolic  mirrors 
with  suitable  receivers.  His  studies  resulted  in 
1869  in  his  invention  of  a  mirror  of  conical  form, 
in  the  focal  line  of  which  he  placed  a  blackened 
metallic  vessel  covered  by  a  thin,  clear  glass  jar 
to  hold  the  heat  which  the  rays  of  the  sun  poured 
through  its  transparent  sides  upon  the  vessel. 
There  he  cooked  beef  a  la  mode  in  1^/2  hours; 
potatoes  in  an  hour ;  baked  bread  in  three-quarters 
of  an  hour,  broiled  (roasted)  beef  in  22  minutes, 
saving  its  juice  in  the  bottom  of  the  pot. 

In  1868  Ericsson  announced  that  he  had  con- 


ITS    PRACTICAL   APPLICATIONS         37 

structed  three  small  solar  engines,  upon  which 
he  and  some  others  based  the  claim  that  he  was 
earlier  in  his  discoveries  than  Mouchot.  But 
careful  investigation  must  lead  any  person  to 
award  priority  both  of  design  and  construction 
to  Mouchot. 

In  October,  1875,  he  reported  to  the  French 
Academy  of  Science  an  apparatus  of  which  his 
book  presents  a  full  description  and  figure. 

The  government  assisted  him  from  time  to 
time,  and  sent  him,  in  1877,  to  Algeria  for  ex- 
tended observations  in  this  line,  which  he  also 
reports.  On  his  return  they  voted  him  a  liberal 
sum  of  money  to  enable  him  to  construct  his 
culminating  success,  the  engine  which  he  ex- 
hibited at  the  Exposition  in  Paris  in  1878. 

We  give  a  copy  of  his  own  illustration  of  this 
great  work. 

Those  of  our  readers  who  do  not  read  French 
will  probably  have  no  difficulty  in  understanding 
the  important  features  of  the  apparatus. 

The  mirror  had  an  opening  of  about  20  square 
metres  (say  a  circular  opening  13^  feet  in 
diameter).  The  boiler,  6j^  feet  long,  had  a 


38  SOLAR   HEAT 

capacity  of  about  21  gallons,  into  which  water 
to  the  amount  of  16  gallons  was  poured,  while 
the  remaining  space  was  left  for  steam. 

Placed  in  the  sun  at  Trocadero  (Paris), 
September  2,  1878,  in  half  an  hour  its  water  was 
boiling  and  the  pressure  of  6  atmospheres  was 
quickly  reached.  The  2Qth  of  September,  with 
a  clear  sky,  at  11.30  A.  M.,  a  pressure  of  7 
atmospheres  was  attained,  and  he  produced  the 
first  block  of  ice  ever  made  by  the  heat  of  the  sun. 
Other  most  satisfactory  achievements  followed 
during  that  month  and  the  next,  in  cooking,  dis- 
tilling, pumping,  etc.,  etc.  The  Exposition 
awarded  him  a  medal. 


FIRST    UNITED    STATES    PATENT. 

/ 

In  the  United  States,  the  first  patent  for  solar 
apparatus  was  issued  March  20,  1877,  to  John  S. 
Hittell  and  George  W.  Deitzler,  of  San  Fran- 
cisco, Cal.  Their  patent  describes  a  "  concave 
mirror,  with  which  they  throw  focalized  heat 
upon  a  mass  of  iron  or  other  suitable  material 

v  i 


ITS    PRACTICAL   APPLICATIONS        39 

as  a  reservoir  of  the  heat;  a  reservoir  chamber, 
a  heat  box,  a  drying  chamber,"  etc.,  letting  the 
cold  air  pass  in  and  then  pass  out  again  after 
the  sun  has  heated  it,  applying  it  then  to  ordi- 
nary hot-air  machinery.  Mr.  Deitzler  took  out  a 
second  patent  May  19,  1882,  in  which  he  de- 
scribed "  a  reflecting  mirror,  straight  one  way, 
curved  the  other  "  —  half  of  a  tube  or  cylinder, 
if  you  please  (what  we  elsewhere  call  a  cylin- 
drical mirror),  and  in  the  line-focus  thus  formed 
he  placed  a  tube  rilled  with  the  material  to  be 
heated.  In  both  patents  the  ordinary  methods 
were  used  to  keep  the  apparatus  facing  the  sun. 
These  gentlemen  deserve  to  be  enrolled  high 
on  the  walls  of  the  true  Temple  of  Fame  for 
their  contributions  to  the  development  of  solar 
calorics.  Mr.  Hittell  had  previously  earned  the 
gratitude  of  his  fellow  citizens  by  his  admirable 
book,  "  The  Resources  of  California,"  which  did 
a  great  deal  to  acquaint  the  world  with  the  fruit 
and  grain  capabilities  of  the  State,  and  its  other 
advantages,  attracting  both  immigration  and 
capital  to  the  coast.  Mr.  Deitzler  entered  very 
practically  into  the  subject,  with  a  mechanical 


40  SOLAR  HEAT 

GRAND  G£N£RATEUR  SOLAIRE  INDUSTRIEL 

EXPOSfi 

Dans  le  Pare  du  Trocade'ro 
(Annexe  de  f  Exposition  AlgJrienne) 

ET   RECOMPENSE   D'UNE   MEDAILLE   D5OR 
LEGENDE 

M.  Secteur  permettant,  au  moyen  de  la  vis  w,  d'incliner 
1'appareil  suivant  la  latitude  du  lieu  cm  Pon  opere. 

N.  Mouvement  a  la  cardan  permettant,  par  Pintermedi- 
aire  des  pignons  d'angle,  de  la  roue  r  et  du  secteur  vu  de 
profil  sur  la  figure  ci-contre,  d'orienter  1'appareil  du  lever 
au  coucher  du  soleil. 

S.  Secteur  permettant,  au  moyen  de  la  vis  o,  d'incliner 
1'appareil  suivant  Pepoque  de  Pannde  ou  Pon  expeVimente. 

F.  Chaudiere  tubulaire  entoure'e  du  manchon  de  verre. 

H.  Dome  de  vapeur. 

I.  Soupape  de  surete*. 

La  vis  ci-contre  munie  d'un  volant  servait  de  contrevente- 
ment  a  1'appareil  une  fois  place*  suivant  1'angle  de  la  latitude. 
Le  refle*teur  compose*  de  fers  a  T  supportant  les  plaques 
rdfldchissantes  dtait  fix€  sur  la  base  en  fonte  de  la  chaudiere. 
Cette  derniere,  composde  de  tubes  en  fer  avait  une  capacite' 
de  100  litres,  70  pour  Peau,  30  pour  la  vapeur.  Son  alimen- 
tation se  faisait  au  moyen  d'un  injecteur. 


ITS   PRACTICAL   APPLICATIONS 


GRAND    GENERATEUR    SOLAIRE  INDUSTRIE!, 
PAR   PROF.   A.    MOUCHOT  (1878) 


42  SOLAR   HEAT 

skill  and  business  energy  which  attracted  the 
attention  of  a  considerable  number  of  men  of 
affairs  to  this  matter. 

THE   SOLAR   HEAT    POWER    COMPANY   OF 
CALIFORNIA 

was  formed  in  1883,  of  which  Wm.  H.  Birch, 
A.  F.  Knorp,  Geo.  A.  Dickson,  Geo.  W.  Deitzler, 
and  H.  C.  Biggs  were  directors,  with  Oscar 
Hines  secretary,  which  both  expressed  and  in- 
creased general  interest  in  the  matter.  [See  San 
Francisco  Bulletin,  March  12,  1883.]  The  death 
of  "  General  Deitzler  "  interfered  with  the  suc- 
cess of  the  company  somewhat. 

The  second  patent  issued  by  our  government 
in  this  department  was  given  April  27,  1880,  to 
James  P.  Mauzey,  of  Blackfoot,  Montana;  whose 
design  was  substantially  a  framework  of  rectan- 
gular form,  with  mirrors  arranged  on  its  (inner) 
walls,  all  so  placed  as  to  concentrate  their  rays 
on  the  focal  point  or  region,  where  he  put  the 
substance  or  article  to  be  heated.  Of  this 


ITS   PRACTICAL   APPLICATIONS         43 

gentleman  the  writer  has  failed  to  learn  any 
particulars.  Another  patent  for  solar-heating 
devices  was  obtained  by  Pacific  coast  men  from 
the  British  government.  Eusebius  J.  Molera  and 
John  C.  Cebrian,  of  San  Francisco,  Cal.,  were  the 
persons,  and  the  date  of  the  issue  of  their  patent 
was  October  22,  1880.  No  special  interest  at- 
taches to  the  specific  designs  they  described.  Of 
them  and  their  work  the  writer  is  also  unable  to 
learn  anything;  yet  they  and  Mr.  Mauzey  must 
not  be  forgotten  in  the  coming  years  of  triumph 
which  await  the  cause  of  solar  heat  utilization. 

In  December,  1883,  W.  Calver,  of  Washing- 
ton, D.  C.,  patented  a  car  containing  interior 
reflecting  surfaces,  which  revolved  on  a  circular 
track,  so  as  to  face  the  sun. 

Another  name  which  deserves  to  be  placed 
high  on  the  roll  of  the  fostering  friends  of  solar 
enginery  is  that  of  Captain  John  Ericsson,  of 
New  York  City,  the  renowned  inventor  and 
builder  of  the  Monitor.  He  was  a  builder  of 
hot-air  engines  and  other  mechanical  construc- 
tions. He  made  elaborate  experiments ;  invented 


44  SOLAR   HEAT 

an  instrument  for  the  measurement  of  the  heat 
which  comes  from  the  sun ;  also  designed  a  boiler 
and  engine  for  the  operation  of  machinery  by 
solar  heat,  a  cut  of  which  we  reproduce  from 
the  Scientific  American  of  May  5,  1877,  by  per- 
mission of  the  publishers.  He  calculated  that 
"  the  heat  radiated  by  the  sun  during  nine  hours 
per  day,  for  all  the  latitudes  comprised  between 
the  equator  and  the  forty-fifth  parallel,  corre- 
sponds per  minute  and  per  square  foot  of 
normal  surface  to  3.5  thermo  units  of  772  foot 
pounds.  This  would  give  a  power  of  270.000 
foot  pounds,  or  from  8  to  9  horse  power  on  a 
surface  of  100  square  feet.  The  engine  illus- 
trated was  built  on  the  caloric  system,  and  had 
run  at  420  revolutions  per  minute,  with  the  sun 
near  the  zenith  and  during  fine  weather." 

By  the  kindness  of  Mr.  T.  M.  McDonough, 
of  Montclair,  N.  J.,  our  attention  was  called  to 
the  following  article  contributed  by  Captain 
Ericsson  to  Nature,  and  there  printed  January  3, 
1884;  reprinted  in  the  Scientific  American  of 
February  2,  1884,  describing  his  second  design. 


ERICSSON'S  SUN  MOTOR,  ERECTED  AT  NEW  YORK,  1883 


ITS   PRACTICAL   APPLICATIONS         47 

"  THE    SUN    MOTOR    AND    THE    SUN'S    TEM- 
PERATURE. 

"  The  annexed  illustration  represents  a  per- 
spective view  of  a  sun  motor  constructed  by  the 
writer  and  put  in  operation  last  summer.  This 
mechanical  device  for  utilizing  the  sun's  radiant 
heat  is  the  result  of  experiments  conducted  dur- 
ing a  series  of  twenty  years;  a  succession  of 
experimental  machines  of  similar  general  design, 
but  varying  in  detail,  having  been  built  during 
that  period.  The  leading  feature  of  the  sun 
motor  is  that  of  concentrating  the  radiant  heat  by 
means  of  a  rectangular  trough  having  a  curved 
bottom  lined  on  the  inside  with  polished  plates, 
so  arranged  that  they  reflect  the  sun's  rays 
toward  a  cylindrical  heater  placed  longitudinally 
above  the  trough.  This  heater,  it  is  scarcely 
necessary  to  state,  contains  the  acting  medium, 
steam  or  air,  employed  to  transfer  the  solar 
energy  to  the  motor;  the  transfer  being  effected 
by  means  of  cylinders  provided  with  pistons  and 
valves  resembling  those  of  motive  engines  of  the 
ordinary  type.  Practical  engineers,  as  well  as 


48  SOLAR   HEAT 

scientists,  have  demonstrated  that  solar  energy 
cannot  be  rendered  available  for  producing  mo- 
tive power,  in  consequence  of  the  feebleness  of 
solar  radiation.  The  great  cost  of  large  reflect- 
ors, and  the  difficulty  of  producing  accurate 
curvature  on  a  large  scale,  besides  the  great 
amount  of  labor  called  for  in  preventing  the  pol- 
ished surface  from  becoming  tarnished,  are  ob- 
jections which  have  been  supposed  to  render 
direct  solar  energy  practically  useless  for  pro- 
ducing mechanical  power. 

"  The  device  under  consideration  overcomes 
the  stated  objections  by  very  simple  means,  as 
will  be  seen  by  the  following  description.  The 
bottom  of  the  rectangular  trough  consists  of 
straight  wooden  staves,  supported  by  iron  ribs 
of  parabolic  curvature  secured  to  the  sides  of  the 
trough.  On  these  staves  the  reflecting  plates, 
consisting  of  flat  window  glass  silvered  on  the 
under  side,  are  fastened.  It  will  be  readily  under- 
stood that  the  method  thus  adopted  for  concen- 
trating the  radiant  heat  does  not  call  for  a 
structure  of  great  accuracy,  provided  the  wooden 
staves  are  secured  to  the  iron  ribs  in  such  a 


ERICSSON'S    SOLAR    CALORIC    ENGINE 


ITS   PRACTICAL   APPLICATIONS         51 

position  that  the  silvered  plates  attached  to  the 
same  reflect  the  solar  rays  toward  the  heater. 
Fig.  2  represents  a  transverse  section  of  the  lat- 
ter, part  of  the  bottom  of  the  trough,  and  sec- 
tions of  the  reflecting  plates,  the  direct  and 
reflected  solar  rays  being  indicated  by  vertical 
and  diagonal  lines. 

"  Referring  to  the  illustration,  it  will  be  seen 
that  the  trough,  n  feet  long  and  16  feet  broad, 
including  a  parallel  opening  in  the  bottom,  12 
inches  wide,  is  sustained  by  a  light  truss  attached 
to  each  end,  the  heater  being  supported  by  verti- 
cal plates  secured  to  the  truss.  The  heater  is 
6%  inches  in  diameter,  n  feet  long,  exposing 
130  x  9.8 — 1,274  superficial  inches  to  the  action 
of  the  reflected  solar  rays.  The  reflecting  plates, 
each  3  inches  wide  and  26  inches  long,  intercept 
a  sunbeam  of  130  x  180 — 23,400  square  inch  sec- 
tion. The  trough  is  supported  by  a  central 
pivot,  round  which  it  revolves.  The  change  of 
inclination  is  effected  by  means  of  a  horizontal 
axle  —  concealed  by  the  trough  —  the  entire 
mass  being  so  accurately  balanced  that  a  pull  of 
5  pounds  applied  at  the  extremity  enables  a  per- 


52  SOLAR   HEAT 

son  to  change  the  inclination  or  cause  the  whole 
to  revolve.  A  single  revolution  of  the  motive 
engine  develops  more  power  than  needed  to  turn 
the  trough  and  regulate  its  inclination  so  as  to 
face  the  sun  during  a  day's  operation. 

"  The  motor  shown  by  the  illustration  is  a 
steam-engine,  the  working  cylinder  being  6 
inches  in  diameter  with  8  inches  stroke.  The 
piston-rod,  passing  through  the  bottom  of  the 
cylinder,  operates  a  force-pump  of  5  inches  diam- 
eter. By  means  of  an  ordinary  cross-head  se- 
cured to  the  piston-rod  below  the  steam  cylinder, 
and  by  ordinary  connecting  rods,  motion  is  im- 
parted to  a  crank  shaft  and  fly  wheel,  applied  at 
the  top  of  the  engine  frame;  the  object  of  this 
arrangement  being  that  of  showing  the  capability 
of  the  engine  to  work  either  pumps  or  mills.  It 
should  be  noticed  that  the  flexible  steam-pipe  em- 
ployed to  convey  the  steam  to  the  engine,  as  well 
as  the  steam-chamber  attached  to  the  upper  end 
of  the  heater,  have  been  excluded  in  the  illustra- 
tion. The  average  speed  of  the  engine  during  the 
trials  last  summer  was  120  turns  per  minute,  the 
absolute  pressure  on  the  working  piston  being 


ITS    PRACTICAL    APPLICATIONS         53 

35  pounds  per  square  inch.  The  steam  was 
worked  expansively  in  the  ratio  of  i  to  3,  with 
a  nearly  perfect  vacuum  kept  up  in  the  condenser 
enclosed  in  the  pedestal  which  supports  the  engine 
frame. 

"  In  view  of  the  foregoing,  experts  need  not 
be  told  that  the  sun  motor  can  be  carried  out  on 
a  sufficient  scale  to  benefit  very  materially  the 
sunburnt  regions  of  our  planet. 

"  With  reference  to  solar  temperature,  the 
power  developed  by  the  sun  motor  establishes 
relations  between  diffusion  and  energy  of  solar 
radiation,  which  show  that  Newton's  estimate 
of  solar  temperature  must  be  accepted. 

"  The  following  demonstration,  based  on  the 
foregoing  particulars,  will  be  readily  compre- 
hended. The  area  of  a  sphere  whose  radius  is 
equal  to  the  earth's  mean  distance  from  the  sun 
being  to  the  area  of  the  latter  as  214.$*  :i,  while 
the  reflector  of  the  solar  motor  intercepts  a  sun- 
beam of  23,400  square  inches  section,  it  follows 
that  the  reflector  will  receive  the  heat  developed 
by  0.508  square  inch  of  the  solar  surface. 
Hence,  as  the  heater  of  the  motor  contains 


54  SOLAR   HEAT 

1,274  square  inches,  we  establish  the  fact  that  the 
reflected  solar  rays,  acting  on  the  same,  are 
diffused  in  the  ratio  of  1,274:0.508 — 2,507:1. 
Practice  has  now  shown  that,  notwithstanding 
this  extreme  diffusion,  the  radiant  energy  trans- 
mitted to  the  reflector,  by  the  sun,  is  capable  of 
imparting  a  temperature  to  the  heater  of  520°  F. 
above  that  of  the  atmosphere.  The  practical 
demonstration  thus  furnished  by  the  sun  motor 
enables  us  to  determine  with  sufficient  exactness 
the  minimum  temperature  of  the  solar  surface. 
It  also  enables  us  to  prove  that  the  calculations 
made  by  certain  French  scientists,  indicating 
that  solar  temperature  does  not  exceed  the 
temperatures  produced  in  the  laboratory,  are 
wholly  erroneous.  Had  Pouillet  known  that  solar 
radiation,  after  suffering  a  two  thousand  five 
hundred  and  sevenfold  diffusion,  retains  a  radi- 
ant energy  of  520°  F.,  he  would  not  have 
asserted  that  the  temperature  of  the  solar  surface 
is  1,760°  C.  Accepting  Newton's  law  that  'the 
temperature  is  as  the  density  of  the  rays/  the 
temperature  imparted  to  the  heater  of  the  sun 
motor  proves  that  the  temperature  of  the  solar 


ITS   PRACTICAL   APPLICATIONS         55 

surface  cannot  be  less  than  520°  x  2,507 — 1,303,- 
640°  F.  Let  us  bear  in  mind  that,  while  at- 
tempts have  been  made  to  establish  a  much  lower 
temperature  than  Newton's  estimate,  no  dem- 
onstration whatever  has  yet  been  produced  tend- 
ing to  prove  that  the  said  law  is  unsound.  On 
the  contrary,  the  most  careful  investigations 
show  that  the  temperature  produced  by  radiant 
heat  emanating  from  incandescent  spherical  bod- 
ies diminishes  inversely  as  the  diffusion  of  the 
heat  rays.  Again,  the  writer  has  proved  by  his 
vacuum  actinometer,  enclosed  in  a  vessel  main- 
tained at  a  constant  temperature  during  the  ob- 
servations, that  for  equal  zenith  distance  the 
intensity  of  solar  radiation  at  midsummer  is 
5.48°  F.  less  than  during  the  winter  solstice. 
This  diminution  of  the  sun's  radiant  heat  in 
aphelion,  it  will  be  found,  corresponds  within 
0.40°  of  the  temperature  which  Newton's  law 
demands.  It  is  proposed  to  discuss  this  branch 
of  the  subject  more  fully  on  a  future  occasion. 
"  The  operation  of  the  sun  motor,  it  will  be 
well  to  add,  furnishes  another  proof  in  support 
of  Newton's  assumption  that  the  energy  increases 


56  SOLAR   HEAT 

as  the  density  of  the  rays.  The  foregoing  ex- 
planation concerning  the  reflection  of  the  rays  — 
see  Fig.  2  —  shows  that  no  augmentation  of 
temperature  takes  place  during  their  transmission 
from  the  reflector  to  the  heater.  Yet  we  find  that 
an  increase  of  the  number  of  reflecting  plates 
increases  proportionally  the  power  of  the  motor. 
Considering  that  the  parallelism  of  the  rays 
absolutely  prevents  augmentation  of  temperature 
during  the  transmission,  it  will  be  asked :  What 
causes  the  observed  increase  of  mechanical 
power?  Obviously,  the  energy  produced  by  the 
increased  density  of  the  rays  acting  on  the  heater. 
The  truth  of  the  Newtonian  doctrine,  that  the 
energy  increases  as  the  density  of  the  rays,  has 
thus  been  verified  by  a  practical  test  which  can- 
not be  questioned. 

"  It  is  scarcely  necessary  to  observe  that  our 
computation  of  temperature — 1,303.640°  F. — 
does  not  show  maximum  solar  intensity,  the  fol- 
lowing points,  besides  atmospheric  absorption, 
not  having  been  considered :  ( i )  The  diminution 
of  energy  attending  the  passage  of  the  heat  rays 
through  the  substance  of  the  reflecting  plates; 


ITS    PRACTICAL    APPLICATIONS         57 

(2)  the  diminution  consequent  on  the  great 
amount  of  heat  radiated  by  the  blackened  surface 
of  the  heater;  (3)  the  diminution  of  tempera- 
ture in  the  heater  caused  by  convection. 

"J.  ERICSSON." 

After  Mr.  Ericsson's  death,  there  was  consid- 
erable disappointment  felt  by  his  admirers  that 
no  complete  development  of  his  inventions  in 
this  department  was  found  among  his  effects;  it 
would  appear  that  advancing  years  prevented 
that  great  concentration  of  his  faculties  on  this 
point,  which  had  made  him  so  successful  in  the 
building  of  the  Monitor,  and  which  might  have 
wrought  greater  success  in  the  arts  of  peace  had 
he  lived  to  develop  all  he  had  planned. 

INDIA    OFFERS    A    FINE    FIELD    FOR    THE    UTILIZA- 
TION   OF    SOLAR    HEAT. 

Mr.  W.  Adams,  an  English  resident  of  Bom- 
bay, India,  made  very  diligent  study  of  this  sub- 
ject, and  developed  an  apparatus  for  which  he 
obtained  a  patent.  A  public  trial  of  his  invention 


58  SOLAR   HEAT 

was  made  at  Bombay  in  presence  of  officials  and 
representatives  of  the  press  and  others.  In  The 
Times  a  full  account  of  the  exhibition  was  pre- 
sented, and  this  was  reprinted  in  the  Scientific 
American  of  June  5,  1878;  two  weeks  later  the 
latter  paper  published  a  letter  from  Mr.  Adams, 
detailing  many  interesting  facts  about  the  mat- 
ter, and  presenting  a  cut  of  the  apparatus.  We 
reprint  these  by  permission  of  Messrs.  Munn  & 
Co. 

"  COOKING  BY  SOLAR   HEAT. 

"  To  the  Editor  of  the  S dentine  'American: 

"  I  send  you  a  short  account  of  my  experi- 
ments, made  in  Bombay,  on  the  utilization  of 
solar  heat  for  cooking.  The  accompanying  en- 
graving will  give  an  idea  of  the  principle  of  the 
cooking  apparatus.  It  consists  of  a  conical  re- 
flector, A,  made  of  wood  and  lined  with  common 
silvered  sheet  glass.  Inside  there  is  placed  a 
copper  cylindrical  vessel,  B,  covered  by  a  glass 
cover,  C.  The  cooking  vessel  is  raised  about 
four  inches  from  the  bottom,  and  the  glass  cover 
is  five  inches  longer  than  the  vessel,  and  two 


ITS    PRACTICAL   APPLICATIONS         61 

inches  wider,  which  leaves  an  interval  of  four 
inches  of  hot  air  under  the  boiler,^  and  one  inch 
all  round  and  at  the  top.  The  wedge  under  the 
apparatus  is  to  keep  it  inclined,  so  that  the  rays 
of  the  sun  may  fall  perpendicularly  on  the  boiler. 
Glass  being  diathermanous  to  the  direct  or  re- 
flected rays  of  the  sun,  and  non-diathermanous 
to  obscure  heat,  the  rays  penetrate  the  glass,  and, 
striking  on  the  vessel,  become  transformed  into 
obscure  heat,  when  they  are  retained  by  the  glass. 
The  glass  cover  over  the  boiler  is  made  octagonal, 
because,  in  that  form,  common  window  glass  can 
be  used.  Of  course  a  glass  dome,  such  as  is  used 
for  covering  clocks  or  statuettes,  would  be  better, 
and,  equally,  of  course,  a  copper  reflector  electro- 
plated with  silver  would  be  better  than  my  re-« 
flector;  but  both  of  these  articles  are  made 
octagonal  in  order  that  cheap  material  may  be 
employed.  The  position  of  the  apparatus  re- 
quires to  be  changed  about  every  half-hour,  to 
face  the  sun  in  its  apparent  course  from  east  to 
west. 

"  The  rations  of  seven  soldiers,  consisting  of 
meat  and  vegetables,  are  thoroughly  cooked  by 


62  SOLAR   HEAT 

it  in  two  hours,  in  January,  the  coldest  month 
of  the  year  in  Bombay,  and  the  men  declare  the 
food  to  be  cooked  much  better  than  in  the  ordi- 
nary manner.  Several  people  in  Bombay  and  in 
the  Deccan  have  tried  it,  and  always  with  success. 
If  the  steam  be  retained,  the  dish  is  a  stew  or 
a  boil;  if  it  be  allowed  to  escape,  the  food  is 
baked. 

"  The  reflector  is  two  feet  four  inches  in 
diameter.  The  intensity  of  the  heat  is  increased 
by  increasing  the  diameter  of  the  reflector.  One 
advantage  of  this  apparatus  is  that  the  food  will 
keep  hot  for  a  long  time  after  the  apparatus  has 
been  withdrawn  from  the  solar  rays.  I  withdrew 
it  at  4  p.  M.,  brought  it  into  a  room,  and  threw 
a  railway  rug  over  it.  At  8  P.  M.,  when  it  was 
uncovered,  the  metal  vessel  was  too  hot  to  be 
handled  by  the  bare  hand.  I  have  a  letter  from 
a  surgeon-general  in  the  service,  which  informs 
me  that  he  cooked  a  leg  of  mutton  in  it,  and 
that  it  '  kept  hot  for  four  hours  '  after  having 
been  removed  from  the  air. 

"  I  am  getting  one  made  six  feet  in  diameter, 
which  will  differ  from  that  represented  in  the 


ITS  PRACTICAL   APPLICATIONS          63 

engraving  by  consisting  of  fourteen  flat  glasses 
instead  of  eight,  and  by  having  an  angle  of  45° 
until  it  is  on  a  level  with  the  middle  of  the 
vessel,  and  thence  upward  an  angle  of  about  60°, 
by  which  arrangement  the  whole  of  the  rays 
reflected  from  the  silvered  glass  \vill  fall  on  the 
lower  half.  Besides  cooking  food,  I  am  making 
a  series  of  experiments  for  heating  steam-boilers 
by  concentrating  the  rays  of  the  sun  upon  them. 
"  For  this  purpose  I  use  a  combination  of  flat 
mirrors,  of  common  sheet  glass,  silvered,  fixed 
in  rectangular  frames  so  as  to  concentrate  the 
solar  rays  to  a  focus  at  a  distance  of  20  feet. 
The  focus  is  about  2  feet  in  diameter.  The  plan 
is  on  the  same  principle  as  that  of  Archimedes, 
by  which  he  burned  the  Roman  fleet,  which, 
under  Marcellus,  was  blockading  Syracuse  — 
the  same  plan  as  that  suggested  by  Anthemius 
of  Tralles  in  the  problems  by  which  he  proved 
the  exploit  of  Archimedes  to  be  possible;  and  as 
that  suggested  by  Kircher,  and  in  1747  adopted 
by  Buffon.  With  72  pieces  of  silvered  sheet 
glass,  each  15  x  iol/2  inches,  at  midday,  in  the 
month  of  May,  a  focus  was  formed,  at  a  distance 


64  SOLAR   HEAT 

of  20  feet,  of  a  temperature  above  1,088°  F.  I 
arrived  at  that  estimate  as  follows:  18  glasses 
raised  the  mercury  in  the  thermometer  to  360° ; 
36  glasses  raised  it  to  over  644°,  when  the  mer- 
cury entered  into  ebullition,  and  consequently 
any  further  rise  could  not  be  registered.  The 
ebullition  of  the  mercury  was  very  violent. 
Placing  the  temperature  produced  by  the  36 
glasses  at  644°,  the  boiling  point  of  mercury, 
and  deducting  100°  as  the  initial  temperature 
of  the  atmosphere  (the  thermometer  was  in  the 
shade),  there  remain  544°  produced  by  36 
glasses.  The  focus  from  the  remaining  36 
glasses  was  then  added,  making  72  glasses;  and 
I  think  it  may  be  inferred  that  the  temperature 
was  then  above  1,088°.  Every  kind  of  wood 
placed  in  this  focus  was  instantly  ignited,  without 
being,  as  in  BufYon's  experiment,  previously 
smeared  with  tar  and  shreds  of  wool.  A  solid 
cylinder  of  water,  18x8  inches,  contained  in  a 
vertical  copper  vessel,  provided  with  a  steam- 
pipe,  was  then  placed  in  the  focus,  and  it  boiled 
in  exactly  20  minutes.  The  ebullition  was  ex- 
ceedingly violent  In  January  last  I  made  an- 


ITS    PRACTICAL   APPLICATIONS         65 

other  experiment  with  198  glasses,  each  15x1054 
inches,  fixed  in  10  rectangular  frames.  A  cop- 
per boiler  containing  9  gallons  of  cold  water  was 
placed  in  the  focus  at  9.25  A.  M.  It  commenced 
to  boil  in  exactly  30  minutes.  It  was  allowed 
to  boil  for  exactly  i  hour,  and  at  10.55  tne  focus 
was  turned  off,  when  3%  gallons  of  water  were 
found  to  have  been  evaporated. 

"  My  next  experiment  will  be  made  with  about 
500  of  these  glasses,  fixed  in  20  rectangular 
frames,  each  6  feet  by  about  4  feet.  The  focus 
will  be  about  2  feet  in  diameter,  and  (according 
to  the  calculation  made  on  the  basis  of  the  results 
of  the  experiment  with  72  glasses)  the  tempera- 
ture will  be  over  7,616°  F.  The  objects  of  that 
experiment  will  be  to  ascertain  how  soon  after 
sunrise  the  water  can  be  provoked  to  boil,  the 
pressure  that  can  be  obtained  in  a  given  period, 
and  the  quantity  of  water  that  can  be  vaporized 
in  a  given  time,  Other  experiments  will  be  made, 
such  as  exposing  different  metals  to  the  focus, 
etc.  The  boiler  that  will  be  used  on  that  occasion 
is  a  vertical  boiler,  2  feet  7  inches  high  and  16 
inches  in  diameter,  with  an  annular  cylinder  of 


66  SOLAR   HEAT 

water  3  inches  in  diameter  up  to  half  its  height. 
It  is  made  of  beaten  copper,  J4  mcn  thick,  which 
will  stand  any  pressure  that  can  be  produced  in 
a  boiler  of  those  dimensions.  It  is  provided  with 
a  steam-pipe,  a  steam-gauge,  and  a  safety  valve, 
and  with  no  other  fittings.  The  20  frames  will 
stand  in  two  rows  of  10  each,  the  second  row 
on  a  platform  6  feet  6  inches  high,  forming  a 
segment  of  a  circle  of  40  feet  in  diameter. 

"  As  there  is  no  limit  whatever  to  the  number 
of  these  mirrors  that  can  be  used  at  once,  there  is 
none  to  the  intensity  of  heat  that  can  be  produced, 
and  consequently  no  limit  to  the  force  of  the 
steam  that  can  be  generated.  The  cost  of  the 
reflecting  material  is  next  to  nothing,  and  it  is 
almost  everlasting.  There  is  no  mechanical  diffi- 
culty in  keeping  the  focus  on  the  boiler  from 
soon  after  sunrise  to  a  little  before  sunset. 

"  I  am  aware  of  the  force  of  the  objection 
that  the  solar  rays  are  sometimes  intercepted 
by  clouds,  even  in  India;  but  as  an  auxiliary  to 
the  ordinary  boilers,  I  believe  that  solar  heat 
could  be  used  so  as  to  save  at  least  25  per  cent. 
of  coal  throughout  the  year  by  my  plan.  As 


ITS   PRACTICAL   APPLICATIONS         67 

coal  in  the  seaports  of  India  is  never  under  30 
shillings  per  ton,  and  double  that  rate  in  the 
interior,  such  a  saving  would  be  exceedingly 
important.  There  are  many  other  purposes  to 
which  it  could  be  applied  besides  driving  steam 
machinery  or  cooking  food,  such  as  distilling 
and  rectifying  spirits,  etc.  At  Aden,  for  exam- 
ple, the  sun  always  shines,  and  potable  water  is 
only  obtained  by  distilling  it  from  salt  water. 

"  I  shall  be  very  glad  to  have  any  expression 
from  your  readers  upon  the  subject,  especially 
upon  the  result  of  the  experiment  that  I  have 
described.  W.  ADAMS. 

"Bombay,  India" 


FRANCE    CONTINUES    MOUCHOT*S    WORK. 


The  following  very  interesting  article  was 
translated  and  reprinted  in  the  Scientific  'Ameri- 
can of  May  13,  1882,  from  that  valuable  journal, 
La  Nature.  We  reprint  the  article  by  permis- 
sion, reproducing,  also,  the  cut  which  illustrated 
the  original  article.  It  would  be  of  great  interest 
to  us  to  learn  more  about  the  labors  of  M.  Pifre, 


68  SOLAR   HEAT 

who  thus  carried  out  ideas  of  M.  Mouchot,  and 
elaborated  new  applications  of  his  own. 


"  PRINTING    BY    SOLAR    HEAT. 


"  Our  readers  already  know  of  Mr.  Mouchot's 
curious  solar  generators,  and  of  the  remarkable 
experiments  that  have  been  performed  by  that 
ingenious  physicist  for  the  purpose  of  turning 
to  account  that  immense  reservoir  of  heat  and 
motive  power,  the  sun.  Mr.  Abel  Pifre,  an  en- 
gineer, has  recently  taken  up  the  labors  of  Mr. 
Mouchot,  and  has  constructed  upon  the  same 
principles  as  those  employed  by  his  predecessor 
as  the  base  of  his  apparatus,  an  insolator,  which 
gathers  the  heat  of  the  solar  rays  in  the  focus 
of  a  mirror,  and  converts  it  into  mechanical 
motion. 

"  On  the  occasion  of  the  fete  of  the  '  Union 
Franchise  de  la  Jeunesse/  which  occurred  Sun- 
day, August  6,  1882,  in  the  Garden  of  the  Tui- 
leries  at  Paris,  there  was  witnessed  a  remarkable 
experiment  with  Mr.  Pi f re's  latest  improvements 
in  the  solar  generator. 


ITS   PRACTICAL   APPLICATIONS         71 

"  There  was  set  up  on  this  occasion  in  the 
garden,  near  the  large  reservoir,  at  the  foot  of  the 
Jeu  de  Paume  stairs,  an  insolator  that  measured 
3.5  metres  in  diameter  at  the  opening  of  the 
reflector.  The  steam  obtained  in  the  boiler  car- 
ried by  the  reflector  at  its  focus  was  utilized  by 
a  small  verical  motor,  of  30  kilogrammetres 
power,  which  actuated  a  Marinoni  printing-press. 
Although  the  sun  was  not  very  hot,  and  its  radi- 
ation was  interfered  with  by  frequent  clouds, 
the  press  was  able  to  work  with  regularity  be- 
tween one  and  five  o'clock  in  the  afternoon,  and 
to  print  on  an  average  five  hundred  copies 
per  hour  of  a  journal  specially  composed  for 
the  occasion,  and  entitled  Soleil- Journal  (Sun 
Journal).  This  is  not  a  revolution  m  the  art  of 
printing,  but  the  result  is  sufficient  to  allow  us  to 
judge  of  the  services  that  insolators  might  ren- 
der in  latitudes  submitted  to  a  radiation  at  once 
more  active  and  constant. 

"  We  could  not  allow  this  splendid  experiment 
to  pass  without  preserving  a  souvenir  of  it. 
Our  engraving  faithfully  represents  the  arrange- 
ments adopted.  The  Pifre  insolator  is  seen  in 


72  SOLAR   HEAT 

the  centre  of  the  cut,  with  its  large  parabolic  mir- 
ror; the  engine  actuated  by  it  is  figured  at  its 
side ;  while  m  the  foreground  to  the  right  is  seen 
the  Marinoni  press  printing  the  journal.  It 
seems  evident  to  us  that  in  hot  countries  the  use 
of  heliodynamics  ought  sometimes  'to  prove  ef- 
fective and  economical."  —  La  Nature. 

May  13,  1882,  there  appeared  in  the  Ameri- 
can an  account  of  an  invention  wrought  out  by 
Prof.  E.  S.  Morse,  of  Salem,  Mass.,  for  "  Util- 
izing the  Sun's  Rays  in  Warming  Houses."  "  It 
consists  of  a  surface  of  blackened  slate  under 
glass,  fixed  to  the  sunny  side  of  a  house  with 
vents  in  the  walls,  so  arranged  that  the  cold  air 
of  a  room  is  let  out  at  the  bottom  of  the  slate 
and  forced  in  again  at  the  top  by  the  ascending 
heated  column  between  the  slate  and  the  glass." 
The  statement  was  made  that  the  inventor's 
house  at  Salem  was  then  heated  by  the  means 
described  in  fine  weather.  The  idea  thus  brought 
forward  has  been  met  within  recent  years  by 
some  very  practical  devices,  which  are  now  on  the 
market. 

In  the  issue  of  the  American  of  December  30, 


ITS    PRACTICAL   APPLICATIONS         73 

1882,  an  account  is  given  of  the  "  solar  cannon 
of  the  Palais  Royal  in  Paris,  France,  which  is 
fired  by  the  heat  of  the  sun  at  noon,  concentrated 
by  means  of  a  burning  glass,  falling  on  the  pow- 
der priming  of  the  cannon."  The  device  is  very 
ancient;  a  traveller,  Neel,  writing  in  1751,  de- 
scribes it.  The  same  journal,  in  the  number  for 
August  1 8,  1883,  contained  an  appeal,  written 
by  one  who  signed  only  the  letter  "  A,"  intended 
to  awaken  the  public  to  a  sense  of  the  value  of 
solar  heat  utilization.  He  called  attention,  espe- 
cially, to  the  importance  of  the  invention  and 
construction  of  lenses  of  great  size  at  moderate 
cost,  reminding  the  reader  that  the  concentra- 
tion of  solar  heat  would  not  require  anything 
like  the  exact  and  achromatic  degree  of  nicety 
which  astronomical  work  demands. 

A  contribution  of  no  slight  consequence  to 
this  subject  appeared  in  the  Scientific  American 
October  3,  1885,  translated  from  La  Nature.  We 
copy  the  article  and  illustration  by  permission. 


74  SOLAR   HEAT 

"THE  UTILIZATION  OF  SOLAR  HEAT  FOR  THE 
ELEVATION  OF  WATER. 

"  This  article  will  treat  of  the  combined  appli- 
cation of  two  natural  forces  to  the  elevation 
of  water.  These  forces  are:  first,  the  heat  of 
the  atmosphere;  and  second,  the  comparatively 
low  temperature  of  the  water  to  be  raised. 

"  The  accompanying  drawing  shows  the  gen- 
eral arrangement  of  an  apparatus  worked  on  this 
principle.  This  apparatus  has  been  built  at 
Auteuil,  where  it  operates  very  well,  although 
our  climate  is  not  favorable  to  the  operation  of 
such  a  device. 

"  F  is  a  small  building  covered  by  a  roof,  E, 
which  is  exposed  to  the  south,  and  this  roof  is 
formed  of  ten  metallic  plates,  which  are  num- 
bered i,  2,  3,  4,  5,  6,  7,  8,  9,  10.  Each  of  these 
plates  consists  of  two  sheets  of  iron  riveted  to- 
gether on  all  their  edges,  and  separated  slightly 
by  filling  pieces.  Each  plate  thus  constitutes  a 
water-tight  receptacle,  in  which  a  volatile  liquid 
can  be  held.  Various  liquids  can  be  used,  but  I 
prefer  a  solution  of  ammonia.  Under  the  influ- 


ITS   PRACTICAL  APPLICATIONS         75 

ence  of  atmospheric  heat,  the  solution  emits 
vapors,  and  said  vapors  or  gases  escape  through 
tubes,  one  of  which  is  provided  for  each  plate, 
and  are  conducted  to  the  receptacle  N.  Any 
liquid  which  may  have  been  carried  along  by 
the  gas  is  taken  back  to  the  plates  by  a  tube. 
By  another  tube  the  gas  escapes  from  the  vessel, 
N.  This  gas  has  a  pressure  of  i,  2,  or  3  atmos- 
pheres, according  to  the  work  which  is  to  be 
done.  It  is  conducted  through  a  tube  to  a  hollow 
sphere,  which  is  placed  in  the  well  or  tank  from 
which  the  water  is  to  be  elevated.  This  sphere 
contains  a  rubber  diaphragm,  which  can  attach 
itself  to  either  half  of  the  sphere. 

"  Let  us  suppose,  for  instance,  that  the  sphere 
is  full  of  water;  the  rubber  diaphragm,  conse- 
quently, will  rest  against  the  upper  half  or  hemi- 
sphere. If,  now,  the  pressure  of  the  ammonia 
gas  is  brought  to  bear  on  the  diaphragm,  it  will 
be  forced  to  rest  on  the  lower  hemisphere;  but 
in  order  to  do  this,  the  diaphragm  must  eject 
the  water  which  fills  the  sphere.  This  causes 
the  formation  of  a  jet  of  water,  as  shown  above 
the  tank,  R,  near  the  letter  G.  But  the  gas  must 


76  SOLAR   HEAT 

be  driven  from  the  sphere  after  it  has  been 
emptied  of  water,  so  that  the  operation  may  be 
renewed. 

"  This  is  accomplished  in  the  following  man- 
ner: In  the  centre  of  the  diaphragm  a  float  is 
inserted,  which  carries  a  rod  by  which  a  slide 
is  actuated.  One  of  the  apertures  in  this  slide 
coincides  with  the  gas  inlet,  and  the  other  with 
the  outlet.  When  the  diaphragm  rests  on  the 
upper  hemisphere  the  inlet  is  opened,  and  the 
water  escapes;  when  it  moves  toward  the  lower 
hemisphere  the  inlet  is  closed,  the  outlet  is 
opened,  the  sphere  is  filled  with  water  again, 
and  so  on. 

"  This  would  complete  the  operation  if  the  am- 
monia gas  did  not  cost  anything,  but  as  it  is 
expensive  it  must  be  used  over  and  over  indefi- 
nitely. Here  we  are  aided  by  the  low  temperature 
of  the  water,  which  is  made  to  pass  through  a 
serpentine  pipe  contained  in  a  water-tight  vessel 
containing  part  of  the  ammonia  solution  used. 
The  solution  is  cooled  by  the  water  in  the  pipe, 
and  is  ready  to  absorb  ammonia.  Then,  as  soon 
as  the  outlet  is  opened,  the  ammonia  gas  con- 


ITS   PRACTICAL   APPLICATIONS         77 

ducted  into  it  is  absorbed,  the  pressure  which  was 
exerted  in  the  sphere  is  removed,  and  water  can 
again  enter  the  sphere. 

"  A  final  precaution  is  taken,  which  is  to  at- 
tach a  little  pump  to  the  float,  by  means  of  which 
the  ammonia  solution  can  be  pumped  back  into 
the  roof,  E. 

"  The  apparatus  at  Auteuil  raises  over  300 
gallons  of  water  per  hour.  In  warm  countries 
the  same  apparatus  would  raise  792  gallons  a 
distance  of  65  feet.  The  calculation  of  the  re- 
sults to  be  obtained  by  this  apparatus  is  based 
on  the  following  considerations: 

"  A  sheet  of  metal  one  yard  square  absorbs  1 1 
calories  for  a  difference  of  one  degree.  Each 
plate  which  has  a  surface  of  4  square  yards  ab- 
sorbs 44  calories  per  hour.  If  there  is  a  differ- 
ence of  6  degrees,  264  calories  will  be  taken  from 
the  atmosphere  every  hour;  and  by  combining 
this  quantity  of  heat  with  the  cooling  action  of 
the  water,  it  is  easy,  by  the  difference  of  tension 
produced,  to  obtain  an  inexpensive  force  for 
raising  water. 

"  This  apparatus  differs  from  the  numerous 


78  SOLAR   HEAT 

devices  by  which  attempts  have  been  made  to 
utilize  solar  heat  by  means  of  the  Archimedean 
mirror,  by  which  only  secondary  heat  is  obtained. 
It  is  not  necessary  to  concentrate  the  heat  by 
metallic  or  other  mirrors;  the  atmospheric  heat 
is  the  basis  of  the  operation,  and  all  roofs  ex- 
posed to  the  sun  can  be  used  for  this  purpose. 
In  this  manner  a  valuable  motive  power  can  be 
obtained  in  warm  countries  without  loss  of  room. 
Generating  plates,  such  as  we  have  described, 
can  be  applied  to  any  roof,  and  if  we  consider 
that  with  only  ten  such  plates  792  gallons  can 
be  raised  65  feet  per  hour,  we  can  easily  under- 
stand that  a  great  elevating  power  can  be  ob- 
tained by  increasing  the  number  of  plates." 

THE   PASADENA  PUMPING  -  ENGINE. 

Prof.  Charles  F.  Holder,  of  California,  widely 
famous  for  his  learning  and  his  writings,  con- 
tributed to  the  Scientific  American  of  March  16, 
1901,  a  very  readable  article  upon  solar  mo- 
te "s.  He  went  over  the  history  of  the  subject 
to  some  extent;  mentioned  a  "burning  mirror," 


THE    PASADENA    PUMPING-ENGINE 
Front  View 


ITS   PRACTICAL  APPLICATIONS        81 

which  was  made  by  a  Frenchman  named  Vil- 
lette,  4  feet  in  diameter,  at  whose  focus  the  heat 
was  so  intense  that  cast-iron  was  melted  there 
in  sixteen  seconds;  that  an  Englishman  named 
Parker  built  a  lens  about  3  feet  in  diameter,  at 
the  focus  of  which  a  cube  of  cast  iron  was  melted 
in  three  seconds,  and  a  block  of  granite  fused  in 
one  minute.  After  other  instances  and  discus- 
sion, he  went  on  to  describe  a  motor  which  had 
been  buildeji^at  the  Ostrich  Farm  in  South  Pasa- 
dena, California. 

"  The  machine  is  exhibited  at  the  Ostrich 
Farm,  and  has  attracted  the  attention  of  a  vast 
number  of  people,  especially  as  Southern  Cali- 
fornia is  now  thronged  with  tourists.  In  appear- 
ance the  motor  resembles  a  huge  disk  of  glass, 
and  at  a  distance  might  be  taken  for  a  windmill 
of  some  kind;  but  the  disk  is  a  reflector  33  feet 
6  inches  in  diameter  on  top,  and  15  feet  on  the 
bottom.  The  inner  surface  is  made  up  of  1,788 
small  mirrors,  all  arranged  so  that  they  can  con- 
centrate the  sun  upon  the  central  or  focal  point. 
Here,  as  shown  in  the  accompanying  illustration, 
is  suspended  the  boiler,  which  is  13  feet  6  inches 


82  SOLAR   HEAT 

in  length,  and  holds  100  gallons  of  water,  leav 
ing  8  cubic  feet  for  steam. 

"  At  the  time  of  the  writer's  visit  to  the  farm 
the  motor  was  the  subject  of  no  little  comment 
and  the  attendant  stated,  confidentially,  that  som 
of  the  questions  were  remarkable.  One  mai 
assumed  that  it  had  something  to  do  with  th 
incubation  of  the  ostrich  eggs;  and  many  aske« 
what  made  it  go,  being  unable  to  understand  o 
appreciate  the  idea.  The  motor  is  attractive  ii 
appearance,  built  lightly,  supported  by  seemingl 
delicate  shafts,  though  in  reality  strong  enoug 
to  resist  a  wind  pressure  of  one  hundred  miles  a: 
hour.  The  reflector  must  face  the  sun  exactl} 
and,  as  heavy  as  it  is,  weighing  tons,  it  can  b 
easily  moved.  It  stands,  after  the  fashion  o 
the  telescope,  upon  an  equatorial  mounting,  th 
axis  being  north  and  south.  The  reflector  fol 
lows  the  sun,  regulated  by  a  clock,  the  work  bein 
automatic,  as,  in  fact,  is  everything  about  11 
The  true  focus  is  shown  by  an  indicator;  and  i 
about  an  hour  after  it  is  adjusted  the  boiler  i 
seen  to  have  attained  a  white  heat,  and  the  stearr 
gauge  registers  150  pounds.  The  steam  is  cai 


THE   PASADENA    PUMPING-ENGINE 
Side  View 


ITS   PRACTICAL   APPLICATIONS        85 

ried  from  the  suspended  boiler  to  the  engine  in 
a  flexible  phosphor-bronze  tube,  and  returns  again 
from  the  condenser  to  the  boiler  in  the  form 
of  water,  so  that  the  boiler  is  kept  automatically 
full.  The  engine  is  oiled  automatically,  and 
when  the  disk  is  once  turned,  facing  the  sun, 
it  runs  all  day  as  independent  of  an  engineer 
as  does  a  windmill. 

"  The  amount  of  heat  concentrated  in  the 
boiler  by  the  seventeen  hundred  and  odd  mirrors 
cannot  be  realized,  as  nothing  can  be  seen  but  a 
small  cloud  of  escaping  steam ;  but  should  a  man 
climb  upon  the  disk  and  attempt  to  cross  it,  he 
would  be  literally  burned  to  a  crisp  in  a  few 
seconds.  Copper  is  melted  in  a  short  time  here, 
and  a  pole  of  wood  thrust  into  the  magic  circle 
flames  up  like  a  match.  That  the  motor  is  a 
success  is  seen  by  the  work  that  it  is  doing  — 
pumping  water  from  a  well,  illustrating  the  pos- 
sibilities of  cheap  irrigation  by  lifting  up  1,400 
gallons  per  minute  —  equal  to  155  miner's  inches. 
Up  to  the  present  time,  the  motor  has  produced 
results  equal  to  about  ten  horse-power,  but  fifteen 
horse-power  is  claimed  for  it. 


86  SOLAR   HEAT 

"  This  motor  is  the  result  of  a  number  of  ex- 
periments by  a  band  of  Boston  capitalists.  One 
of  the  first  productions  was  a  silver  reflector, 
which  cost  many  thousands  of  dollars,  but  was 
abandoned.  The  next  was  modelled  after  the 
Ericsson  machine  of  1884;  but  it  was  a  failure. 
A  third  was  erected  at  Longwood,  proving  also 
a  failure.  A  fourth  attempt  was  made,  this  time 
at  Denver,  Colo.,  which  was  fairly  successful, 
doing  one-half  of  the  work  since  performed  by 
the  Pasadena  model.  This  latter  was  at  length 
produced,  and  found  to  be  a  success. 

.."No  invention  of  modern  times  has  given 
such  an  impetus  to  the  development  of  arid  lands 
as  the  solar  motor,  and  it  has  been  visited  by 
many  interested  in  the  question.  The  develop- 
ment of  Southern  California  has  been  seriously 
hindered  by  the  lack  of  fuel,  the  country  being 
dry  and  barren  in  localities  where  rich  mines  are 
known  to  exist.  The  country  is  cloudless  for 
months,  —  in  every  sense  the  land  for  solar  mo- 
tors, as  water  underlies  the  surface  almost  every- 
where, and,  when  pumped  up  and  sent  out  upon 


ITS   PRACTICAL  APPLICATIONS        87 

the  soil,  the  region  ceases  to  be  a  desert,  and  can 
be  made  to  blossom  as  the  rose." 

A    WORD    FROM    AN    AMERICAN    IN    INDIA. 

June  15,  1901,  there  appeared  in  the  Scientific 
American  a  letter  from  Rev.  Walter  T.  Scudder, 
an  American  missionary  at  Vellere,  in  the  pres- 
idency of  Madras,  India,  which  should  be  noted 
here.  He  seems  not  to  have  known  of  the  ex- 
periments and  successes  of  Mr.  Adams  at  Bom- 
bay in  a  former  year,  nor  of  other  historical 
illustrations  of  solar  heat  in  service;  he  had, 
however,  read  the  article  just  quoted  from  Pro- 
fessor Holder,  and  fully  endorsed  its  reasonings, 
and  accepted  its  testimony  from  the  standpoint 
of  a  resident  in  India.  He  gave  the  results  of 
some  experiments  he  had  made  in  testing  the 
actual  heat  of  the  rays  of  the  sun  by  the  use 
of  ordinary  thermometers.  Hanging  one  in- 
strument in  the  open  air,  where  the  sun  shone  full 
upon  it,  he  placed  another  in  a  cardboard  box, 
covered  with  glass,  through  which  the  rays  of 
the  sun  were  admitted,  the  heated  air  being  en- 


88  SOLAR   HEAT 

closed  by  the  box.  April  7,  1901,  he  found  that 
the  former  thermometer  indicated  126°  R,  and 
the  latter  157° ;  five  days  later,  in  a  similar  trial, 
he  obtained  127°  and  159°.  He  thus  demon- 
strated the  fact  that  the  heat  of  the  sun  may  be 
economized  by  sheltering  and  accumulating  the 
rays.  This  fact  might  have  been  deduced  from 
the  common  practice  of  people  in  cold  countries 
of  using  double  windows  for  the  purpose  of  econ- 
omizing fuel  and  keeping  part  of  the  heat  of  the 
sun  when  it  comes  upon  them.  M.  Mouchot, 
too,  used  this  principle  in  the  glass  cover  which 
he  placed  over  his  boiler  at  the  focus  of  his 
reflector.  The  idea  is  capable  of  very  large  ap- 
plication. 


CHAPTER    II. 

SOME    TECHNICAL   STUDY   OF   THE   SUBJECT. 

LET  me  ask  you  to  note  carefully  at  the  outset 
these  two  points  first,  that  this  treatise  does  not 
concern  itself  at  all  with  the  nature  of  the  sun, 
or  its  rays;  the  orb  may  be  of  flame  or  of  ice; 
the  rays  may  be  dependent  on  or  affected  by 
local  conditions  at  the  sun,  or  by  the  quality  of 
our  atmosphere,  or  both.  None  of  these  partic- 
ulars, these  questions,  affect  the  practical  matter 
we  have  in  hand.  We  find  sunshine  coming  upon 
us;  we  learn  from  experience  that  we  can  get 
heat  from  the  rays  as  they  fall,  and  can  combine 
the  force  of  a  number  of  rays  in  a  beam  of  in- 
creased intensity. 

Our  problems  are  along  these  two  lines :  How 
can  we  best  receive  and  accumulate  the  heat 
89 


90  SOLAR   HEAT 

which  the  sun  brings  to  us  ?  The  "  technical 
study"  here  attempted  is  most  practical  in  its 
quality;  intended  for  the  man  of  the  farm  and 
the  shop  quite  as  much  as  the  man  of  the  school 
or  the  laboratory.  A  future  stage  of  the  art 
will  necessarily  take  up  deep  questions  of  theory 
for  the  higher  development  of  the  subject;  but 
now  and  always  the  chiefly  important  side  of  the 
matter  is  the  practical.  How  can  we  get  and  use 
the  largest  amount  of  solar  heat? 

And,  second,  the  manner  of  treatment  here 
given  to  the  problems  in  hand  is  one  which  aims 
to  inform  the  man  who  has  no  technical  library 
at  hand,  to  aid  the  ranchman  and  the  prospector 
in  devising  offhand  appliances,  as  well  as  to  help 
the  educated  and  skilled  artisan  and  manufacturer 
along  their  paths,  by  a  few  blunt,  crude  hints 
and  by  the  suggestive  force  of  the  historical  ac- 
counts herein  presented. 

NOMENCLATURE. 

What  are  the  proper  terms  to  be  used  in  de- 
scribing the  subject  of  this  discussion? 


ITS   PRACTICAL  APPLICATIONS        91 

The  writer  selected  as  the  title  of  his  former 
work  the  phrase,  "Solar  Enginery"  intending 
to  include  all  appliances  for  the  collection  and 
use  of  the  heat  of  the  sun,  whether  a  simple 
heat-box  or  a  steam-engine,  maintained  by  solar 
caloric.  Some  objection  was  made  by  critics  on 
the  ground  that  the  terms  might  apply  equally 
well  to  a  study  of  the  motion  of  the  sun  and  its 
satellites;  and  because  the  furnace  heated  by 
solar  rays  is  hardly  an  "  engine.'*  Solar  Calorics 
is  a  correct  expression  for  a  treatise  on  the  nature 
and  laws  of  the  heat  derived  from  the  sun;  but 
is  not  suggestive  of  practical  utilities.  "  The 
Utilization  of  Solar  Heat "  is  a  cumbrous  phrase, 
well  enough  for  the  index  to  patents,  but  not 
popular  in  its  sound.  The  well-known  term  of 
the  schools,  Ther mo-dynamics,  would  be  a  good 
title,  but  it  has  so  broad  a  meaning  that  it  does 
not  confine  the  subject  to  the  limits  we  have 
given  ourselves;  Helio-thermo-dynamics  (helios, 
the  sun;  therme,  heat;  and  dnnamis,  power)  is 
the  precise  word  for  us;  only  it  would  not  at- 
tract the  average  reader;  and  this  book  is  made 
for  the  every-day  man,  the  unprofessional,  prac- 


92  SOLAR   HEAT 

tical  person,  who  has  a  clearer  idea  of  English 
than  of  the  Greek  language,  from  which  the 
scientific  terms  have  been  customarily  drawn. 
Solar  Heat:  Its  Practical  Applications,  is  a  title 
which  carries  its  notion  to  any  reader. 

PREMISES. 

1.  The  first  of  the  principles  to  be  stated  is 
this :   We  have  no  power  to  increase  or  diminish 
the  actual  heat  which  comes  to  us  from  the  sun 
at  any  time;   the  regulation  of  that  heat  is  alto- 
gether superior  to  us,  depending  upon  the  state 
of  the  atmosphere,  the  wind,  dust,  clouds,  fog,  or 
other  things  over  which  we  can  never  acquire 
any  control;    we  can  simply  take  what  comes. 
There  is  no  such  thing  as  making  a  greater  fire 
under  our  boilers,   raising  the  temperature  by 
skilful  manipulation  of  the  fire,  except  by  meth- 
ods of  a  secondary  sort  mentioned  below. 

2.  We  are  able,  however,  to  keep  what  we  get ; 
to  fend  off  winds  from  our  apparatus,  to  guard 
our  machinery   from   dust  by   glass   coverings, 
small  or  large,   movable  or   stationary,   as   the 


ITS   PRACTICAL   APPLICATIONS         93 

case  may  demand;  we  can  use  means,  in  case 
it  seems  best,  to  keep  our  articles  or  surfaces 
to  be  heated  facing  the  sun  throughout  the  day, 
so  as  to  avail  ourselves  of  all  that  comes  our 
way;  and  we  can  select  such  localities  as  are 
most  favorable  in  all  respects  for  the  business. 
We  are  also  able,  by  various  methods,  to  connect 
as  many  furnaces  or  engines  as  we  wish,  so  that 
the  heat  of  each  may  contribute  to  a  total  result 
far  larger  than  could  be  attained  by  a  single 
apparatus;  and  we  may  store  up  the  heat  and 
the  power  obtained  from  it  for  use  at  some  other 
time  or  place. 

3.  While  the  rays  of  the  sun  come  to  us  in 
parallel  lines  with  a  uniform  temperature  on 
either  hand,  and  would  heat  every  part  of  an 
exposed  surface  as  hot  as  any  other,  the  laws 
of  heat  rays  are  those  of  undulation  or  wave 
motion  in  general,  the  same  as  those  of  a  ball, 
thrown  on  a  floor,  or  a  beam  of  light  falling 
on  a  table,  or  a  sound-wave  reaching  a  listener. 
These  rays  may,  therefore,  be  gathered  together, 
made  to  unite,  as  if  they  became  one  denser, 
stronger,  hotter  ray,  so  that  the  temperature  of 


94  SOLAR   HEAT 

the  condensed  rays  will  be  raised  in  proportion 
to  the  number  of  rays  blended ;  and  we  can  thus 
cause  the  heat  to  increase  to  any  degree  our 
apparatus  can  be  enlarged.  By  secondary  means, 
then,  we  can  secure  a  hotter  fire  in  our  solar 
furnace  than  there  is  in  the  open  air  or  on  a 
plain  surface.  And  the  art  of  solar  enginery  is 
a  reaching  after  the  best  means  of  thus  taking, 
guarding,  uniting,  and  directing  these  gathered 
rays  for  domestic  and  industrial  uses. 

The  subject  has  four  natural  divisions:  (A) 
The  Reception  of  Solar  Rays,  (B)  The  Reflec- 
tion of  Solar  Rays,  (C)  The  Refraction  of  Solar 
Rays,  (D)  The  Application  of  Solar  Heat. 

(A)  The  Reception  of  Solar  Rays.  First  of 
all,  the  article  which  we  desire  to  heat  must  be 
placed  directly  in  the  path  of  the  beams  of  the 
sun,  at  right  angles  to  that  path.  Almost  any 
material  has  some  tendency  to  refuse  admission 
to  the  heat  of  the  sun,  or,  as  we  say,  to  reflect 
away  part  of  what  falls  upon  it;  therefore,  we 
must  place  it  so  that  the  rays  shall  have  the  best 
opportunity  to  enter  its  very  substance.  The 
best  color  for  the  article  or  receptacle  is  black,  and 


ITS   PRACTICAL   APPLICATIONS         95 

that  free  from  any  sheen  or  gloss  or  polish  what- 
ever. It  is  an  advantage  if  the  surface  be  rough, 
porous,  or  provided  with  openings  of  some  kind 
into  which  the  rays  can  enter  and  be  lost,  so  to 
speak.  The  receptacle  may  be  furnished  with 
a  glass  cover,  which  will  admit  all  the  rays  (or 
nearly  all),  and  will  hold  them  back  from  es- 
caping from  the  surface  after  it  has  become  hot. 
Such  protection  is  particularly  important  in  the 
windy,  dusty  regions,  where  most  solar  machines 
must  be  located.  Glass  houses  —  like  botanical 
conservatories  —  may  be  built  for  this  purpose, 
or  "  sash-beds  "  or  bell-glass  coverings  may  meet 
the  case  sometimes. 

The  article  or  receptacle  to  be  heated  may  re- 
main stationary  or  be  swung  around  at  the  same 
speed  as  the  sun,  keeping  its  face  toward  that  orb 
all  the  day.  Which  course  is  the  better  will  de- 
pend upon  the  nature  of  the  substance  to  be 
heated  and  the  use  to  be  made  of  the  heat.  Many 
cases  will  occur  where  enough  caloric  will  be  ob- 
tained by  simple  "  hello-stats"  i.  e.  stationary 
furnaces  or  ovens.  Even  water-raising  appara- 
tus has  been  made  successful  in  this  way  [see 


96  SOLAR   HEAT 

the  Auteuil  experiment].     There  is  a  large  field 
for  investigation  and  invention  here. 

But  in  most  cases  the  article  or  receptacle 
must  be  made  to  turn  as  the  sun  (apparently) 
turns.  Machinery  must  be  used  which  will  cause 
the  structure  to  revolve  as  fast  as  the  sun  moves. 
As  astronomers  have  "  orienting  "  machinery  to 
keep  their  telescopes  in  the  path  of  the  stars,  so 
we  must  have  gear  to  keep  the  solar  furnace  "  in 
the  eye  of  the  sun."  Two  movements  are  to  be 
regarded;  the  daily  motion  across  the  meridian, 
or  in  a  westerly  course,  and  the  continual  change 
of  the  path  of  the  sun  to  a  more  northerly 
or  southerly  position,  astronomically  speaking. 
That  is  to  say,  during  six  months  the  path  of  the 
sun  is  higher  above  the  horizon  each  day  till  it 
reaches  its  highest,  hottest,  midsummer  altitude; 
then,  during  the  next  six  months,  the  path  is 
daily  lower  and  lower  till  the  lowest,  coldest,  mid- 
winter altitude  is  reached.  (This  statement  is 
entirely  unscientific  in  form,  but  substantially 
accurate. ) 

Our  apparatus,   for  this  reason,  must  be  so 
constructed  as  to  change  its  path  daily,  either 


ITS   PRACTICAL   APPLICATIONS         97 

automatically  or  by  the  hand  of  an  attendant,  if 
we  would  secure  absolutely  exact  reception  of  the 
rays.  But  the  problem  is  easy,  since  a  simple 
turning  over  from  left  to  right  (east  to  west) 
of  a  structure  lying  in  the  meridian,  and  a  daily 
change  of  the  elevation  of  the  northern  end  of 
the  apparatus  is  all  that  is  needful.  Any  man  of 
ordinary  intelligence  can  practically  locate  the 
meridian,  i.  e.  the  true  north  and  south  line,  by 
driving  two  stakes  at  night  in  the  direction  of 
the  North  Star ; l  and  the  latitude  of  the  place, 
subtracted  from  90°,  gives  the  highest  degree 
of  altitude  that  the  sun  will  reach  at  that  point. 
Nature  has  provided  some  admirable  localities 
for  this  business  in  hillsides  that  slope  toward 
the  south;  and  apparatus  may  there  be  placed 
at  an  angle  midway  of  the  local  range  of  altitude 

1  Strictly  speaking,  the  North  Star  is  not  "  fixed."  It  has 
a  rotary  motion  in  an  orbit  of  what  we  may  practically  call 
very  narrow  limits.  To  get  the  precise  meridian,  it  is 
necessary  to  make  a  series  of  observations  upon  the  pole- 
star  so  as  to  get  the  extreme  east  and  west  positions  of  the 
star  and  their  central  or  average  position.  But  for  ordi- 
nary solar  heating  apparatus  the  line  established  by  a 
single  observation  will  be  sufficiently  near  the  true  me- 
ridian. 


98  SOLAR    HEAT 

during  the  season  or  period  when  the  apparatus 
is  to  be  most  used  ;  and  it  will  then  require  very 
little  change  from  day  to  day  in  that  respect. 
As,  at  a  place  in  latitude  39°,  the  receiver  may 
be  located  on  a  slope  which  has  an  inclination 
of  39°  30  min.  ;  because  the  lowest  noon  alti- 
tude of  the  sun  being  23°  less  than  its  highest, 
and  the  middle  point  11°  and  30  min.  below  the 
highest;  subtracting  the  latitude  from  90,  we 
have  51°  as  the  highest  altitude;  23°  below  that 
is  28°  as  the  lowest;  and  39°  30  min.  as  the 
medium. 

THE     REFLECTION     OF     SOLAR     HEAT. 


The  rays  of  the  sun  may  be  brought  to  a 
focus,  gathered  into  a  knot,  directed  to  one  spot, 
made  to  combine  their  energy  on  a  point.  (See 
Ericsson's  discussion  of  this  subject,  page  56). 
Although  we  cannot  increase  the  heat  of  a  ray, 
we  can  increase  the  temperature  of  a  spot  on 
which  a  number  of  rays  thus  unite.  This  is  done, 
sometimes  by  reflection,  i.  e.  by  bending  the  rays 
from  their  course;  if  they  strike  on  a  smooth,  light 
surface,  into  which  they  cannot  enter,  or  which 


ITS    PRACTICAL   APPLICATIONS         99 

they  have  more  tendency  to  turn  away  from  than 
to  penetrate,  they  will  be  bent  away  in  a  new 
direction.  The  course  they  take  will  depend  upon 
the  course  in  which  they  came;  as  the  geomet- 
rical statement  is,  "  The  angle  of  reflection  is 
equal  to  that  of  incidence." 

We  can,  then,  construct  and  arrange  our  re- 
flecting substances  in  such  forms  as  will  bring 
these  newly  directed  rays  of  solar  heat  into  our 
service  most  advantageously. 

The  simplest  form  is  a  Plane  Mirror  (Fig.  i). 
This  does  not  converge  the  rays  at  all,  but  throws 
them  upon  the  exposed  surface  in  a  mass,  which 
will  be  shaped  exactly  like  the  area  of  the  mirror 
if  they  are  reflected  back  in  the  precise  direction 
from  which  they  came;  but,  if  they  are  thrown 
to  one  side,  the  shape  of  the  mass  will  be  changed 
according  to  the  angle  of  reflection,  taking  the 
form  of  a  parallelogram  whose  shorter  diameter 
will  be  reduced  as  the  plane  of  the  reflector  and 
that  of  the  incident  rays  approach  one  another, 
till  it  becomes  almost  a  mere  line.  An  indefinite 
number  of  rays  may  be  massed  by  plane  mirrors, 
although  not  strictly  concentrated. 


100 


SOLAR   HEAT 


\ 


V 


FIGURE    I 


ITS   PRACTICAL   APPLICATIONS       101 

If  we  take  a  plane  mirror  and  bend  it  in  a 
cylindrical  form,  we  may  bring  the  rays  to  a 
line,  more  or  less  accurately  according  to  the 
curvature.  A  parabolic  form  will  secure  the 
closest  approximation  to  this  result  (Fig.  2). 
A  pipe,  or  several  parallel  pipes,  may  be  heated 
by  this  means  to  a  temperature  depending  on  the 
width  of  the  mirror  and  the  perfection  of  the 
reflecting  substance.  Captain  Ericsson's  second 
design  made  use  of  this  law. 

If,  now,  we  construct  a  Concave,  Parabolic 
mirror,  the  rays  will  be  concentrated  on  a  single 
point,  approaching  it  from  all  parts  of  the  mirror. 
Modifications  of  this  form  may  be  made,  by 
which  the  focal  point  may  be  within  the  enclo- 
sure of  the  mirror,  or  at  a  distance  in  front  of  it 

(Fig.  3). 

The  simplest  form  of  this  mirror  is  that  which 
is  used  in  locomotives  to  throw  the  rays  of  a 
lamp  ahead  along  the  track  in  parallel  lines.  This 
use  of  the  reflector  is  exactly  the  opposite  of 
our  application  of  it;  but  the  headlight  reversed 
is  a  striking  illustration  of  the  solar  heating 
apparatus.  This  general  form  —  the  parabolic, 


IO2 


SOLAR   HEAT 


FIGURE   2 


ITS   PRACTICAL   APPLICATIONS       103 


^      s 

^r  /•  s 

A  !  /  Z 

/i  /  /  /  /• 

B3772L 

SSSu. 

r-^ 

X/.'\\\N 

v  n\\  \ 

\J     \    \    \     N 

X\      \     \       X 

^^^       \         ^ 

""*"^\_      X 

^-^s^^^ 

FIGURE   3 


104  SOLAR    HEAT 

concave  mirror  —  may  be  preserved,  while  its 
walls  are  modified;  as  separate,  plane  mirrors 
may  be  arranged  in  a  frame  so  as  to  throw  their 
rays  in  masses  on  a  central  or  focal  spot,  piling 
up  the  heat  on  whatever  one  desires  to  heat. 
Or  segments  of  the  parabola  may  be  made,  each 
a  plane  mirror  (chord  to  the  curve),  bent  in 
only  one  direction  (radially)  to  the  general 
direction  of  parabolic  walls.  The  advantage  of 
the  parabolic  form  is  the  concentration  of  rays 
about  one  point,  losing  none,  but  utilizing  all 
that  fall  on  the  apparatus.  There  is  special  dif- 
ficulty in  the  polishing  of  the  surface  thus  shaped ; 
and  the  construction  also  requires  great  care. 
Mouchot,  after  using  it  in  his  early  engines,  dis- 
carded it  for  a  combination  of  plane  mirrors  in 
a  truncated  cone,  preserving,  however,  the  enclos- 
ing feature  of  the  parabolic  mirror.  Experience 
must  determine  for  each  manufacturer  the  form 
which  best  suits  his  special  purposes. 

Plane  reflectors  may  be  of  great  service  some- 
times. Stand  at  the  sunny  side  of  a  high  board 
fence  which  has  been  whitewashed,  if  you  would 
test  this;  lay  any  article  on  the  ground  by  the 


ITS   PRACTICAL   APPLICATIONS       105 

side  of  such  a  fence,  and  see  how  quickly  it  will 
become  heated,  and  how  very  hot  it  will  get  when 
the  fence  stands  exactly  at  right  angles  to  the 
path  of  the  sun's  rays.  No  doubt,  simple  fences 
of  this  sort,  extending  from  east  to  west  or  from 
north  to  south,  may  be  employed  as  concentrating 
apparatus  for  some  purposes ;  or  a  pair  of  fences, 
inclined  a  little  from  the  perpendicular,  away 
from  each  other,  may  throw  down  a  powerful 
heat  at  their  base. 

THE     MATERIAL    FOR    REFLECTORS. 

The  finest  of  all  reflectors  is  one  of  burnished 
gold;  a  thin  plating  of  gold  upon  a  copper  or 
composition  metal  surface  would  give  almost  as 
perfect  effect.  Next  to  gold  stands  silver.  This 
has  been  used  in  the  arts  a  great  deal  for  reflectors 
of  various  sorts.  Glass  plates,  silvered,  are  very 
practical  and  effective.  Speculum  metal,  an  alloy, 
has  been  employed  for  the  reflectors  of  astronom- 
ical apparatus.  Copper,  burnished,  gives  very 
high  percentage  of  reflection;  tin,  nickel,  and 
other  substances  are  of  value.  White  paper, 


106  SOLAR   HEAT 

especially  when  calendered  or  polished,  may  be 
proved  to  have  considerable  value.  Snow  gives 
surprising  results.  The  writer,  in  Farmington, 
Me.,  in  1883,  dug  a  hole  in  a  snow-drift,  shaping 
it  in  a  general  parabolic  shape  with  a  shovel,  and 
raised  the  thermometer  60°  above  the  tempera- 
ture of  the  surrounding  air  in  a  cold  day.  A 
scientifically  constructed  mirror  of  this  sort,  made 
for  the  Arctic  traveller  or  the  resident  of  a  north- 
ern clime,  and  placed  on  a  sled,  could  be  turned 
to  face  the  sun,  and  obtain  a  temperature  hot 
enough  for  water-boiling  and  cooking  very  easily. 
If  the  sun  can  blind  the  ordinary  traveller  by 
its  glare,  and  cause  violent  optical  disease  to 
those  who  dwell  upon  its  whiteness,  it  can  be 
made  to  atone  for  its  cruelties  by  doing  service 
as  a  fuel  and  a  kinetic. 

Ice  is  as  good  as  snow  for  reflecting  purposes, 
if  not  better.  The  Arctic  explorer  of  the  future 
must  avail  himself  of  these  two  substances  and 
the  heat  of  the  sun  in  the  polar  summer  day, 
with  its  long  duration.  Who  can  tell  what  sur- 
prising results  will  be  attained  when  these  agents 
are  harnessed  in,  more  tractable  than  Esquimaux 


ITS    PRACTICAL  APPLICATIONS       107 

dogs,  less  expensive  than  coal  or  wood,  obtainable 
on  the  largest  scale?  Taking  patterns  from  home, 
carrying  some  portable  apparatus  for  use  when 
not  stationed  at  a  particular  spot,  the  coming 
searcher  for  the  pole  will  go  forth  with  confi- 
dence of  victory. 

Reflectors  have  some  disadvantages.  They  are 
hard  to  make  and  difficult  to  keep  in  order. 
Rust,  dust,  chemical  alteration  of  the  metallic 
surfaces,  the  careless  scratching  done  by  those 
who  undertake  to  clean  them,  the  wild  abrasion 
of  dust-storms  in  some  localities,  —  such  are 
some  of  the  drawbacks  to  their  use.  They  are 
often  very  expensive.  The  weight  of  large  ones 
is  formidable;  the  work  of  repairing  them  may 
require  skilled  workmen,  who  are  not  always 
available;  and  other  troubles  may  assail  the 
owner  of  a  reflecting  heliostat.  But  these  diffi- 
culties are  no  greater  than  the  burdens  which 
a  man  assumes  when  he  buys  or  sets  up  a  steam- 
engine  with  fuel-burning  attachment;  the  trou- 
bles and  expenses  are  of  another  sort,  but  the 
incubus  is  probably  no  heavier  on  the  solar  side. 


io8  SOLAR    HEAT 

And  the  lack  of  cost  for  fuel  will  be  a  large  pre- 
mium on  the  latter  side. 

REFRACTION     OF     SOLAR     HEAT. 

(C)  Solar  rays  move  on  in  a  straight  course 
so  long  as  they  are  passing  through  a  material  of 
uniform  density,  where  the  resistance  offered  to 
their  progress  is  the  same.  But  when  they  pass 
into  a  medium  of  different  density,  they  are  bent 
or  refracted  out  of  their  course.  If  the  body 
through  which  they  now  pass  is  parallel-sided, 
like  a  common  pane  of  glass,  the  rays  resume  their 
former  course  on  leaving  it  (Fig.  4).  If  the  sur- 
face they  entered  was  at  right  angles  to  their  for- 
mer course,  they  suffered  no  change  of  direction 
whatever.  If  it  was  inclined  at  all,  they  were 
set  aside,  so  to  speak,  and  then  restored  to  their 
previous  line  on  leaving.  And  this  is  true,  what- 
ever their  relative  density.  But  if  the  surface 
through  which  a  ray  enters  the  new  medium  is 
inclined  to  the  surface  through  which  it  departs, 
the  ray  takes  a  new  course,  bending  toward  the 
thicker  side  of  the  medium.  We  may  suppose 


ITS   PRACTICAL   APPLICATIONS       109 


Ilill! 


FIGURE  4 


no  SOLAR   HEAT 

that  this  law  applies  to  all  substances  which  are 
diathermous,  whether  they  be  wood,  metal,  solid, 
or  liquid;  perhaps  inventors  may  develop  new 
lenses  out  of  materials  hitherto  never  thought  of 
for  the  purpose.  But  we  can  see  the  effect  of  the 
transmission  of  rays  of  light  and  heat  through 
what  we  call  transparent  substances.  The  best 
of  these  is  crystal  salt,  which  delivers  the  largest 
percentage  of  .the  heat  which  is  given  to  it. 
Quartz  crystal  is  next;  then  come  the  various 
grades  of  glass;  the  latter  are  the  prevalent 
materials  to-day,  because  of  their  comparative 
cheapness.  Glass  vessels,  shaped  as  lenses,  entire 
or  cut,  filled  with  water,  gas  or  any  other  fluid 
which  is  a  good  transmitter  of  the  rays,  furnish 
the  least  expensive  material.  Whatever  the  ma- 
terial, the  laws  of  refraction  are  the  same.  Each 
substance  has  its  peculiar  "  refractive  angle  "  or 
degree  of  turning  the  ray  aside;  each  has  its 
special  clearness  or  opacity.  It  is  the  province 
of  the  manufacturer  to  investigate  these  things, 
and  determine  for  himself  which  material  is  the 
best  for  the  special  class  of  goods  he  is  making; 
sometimes  the  cost  of  raw  materials  may  decide 


ITS   PRACTICAL  APPLICATIONS       in 

the  question;  a  great  many  sorts  of  refractors 
may  be  effective  under  proper  management.  The 
tables  of  diathermacity  are  of  slight  value  com- 
pared with  actual  experiment  and  practical  test 
in  operation. 

If  the  two  surfaces  through  which  a  ray  passes 
are  both  "  plane,"  and  form  an  angle,  the  rays 
passing  through  will  all  be  turned  aside  parallel, 
and  will  fall  in  a  mass  as  the  rays  reflected  by  a 
plane  mirror  (Fig.  5).  This  wedge-shaped  or 
triangular  prism  separates  the  normal  ray  into 
its  separate  (prismatic)  colors,  which  differ  in 
temperature,  the  red  rays  being  hottest ;  but  when 
we  pile  one  of  these  masses  of  rays  upon  another, 
by  refraction  from  a  group  of  prismatic  panes, 
there  is  no  loss  of  heat  by  reason  of  the  disper- 
sion. Indeed  it  will  be  possible  to  obtain  some 
advantage  from  it  if  the  combination  of  refracted 
rays  is  made  with  reference  to  such  a  result. 
If  one  of  the  surfaces  is  plane  and  the  other 
curved  in  a  circular  form  (i.  e.  making  an  arc 
of  a  circle) ,  the  rays  will  be  refracted  to  a  centre 
or  focus;  and,  if  this  circular  surface  is  plane 
in  the  other  direction,  like  a  piece  of  metal  bent 


112 


SOLAR   HEAT 


ITS   PRACTICAL   APPLICATIONS       113 

in  one  direction,  forming  a  partial  cylinder,  then 
the  rays  will  be  focalized  along  a  line.  If  stopped 
by  a  tube  or  pipe,  placed  at  the  focus,  they  will 
heat  the  tube.  Captain  Ericsson's  second  solar 
engine  used  a  reflector  which  gave  this  Neffect; 
other  experimenters  have  reached  the  same  result 
with  piano-cylindrical  lenses,  such  as  we  are  de- 
scribing (Fig.  6). 

If  we  have  a  medium,  one  of  whose  surfaces 
is  plane  and  the  other  convex,  i.  e.  forming  a 
segment  of  a  sphere  or  bounded  by  an  arc 
of  a  circle  in  each  direction,  all  the  rays 
which  enter  at  right  angles  to  the  plane  sur- 
face (whether  that  be  the  entering  or  the  de- 
parting surface)  will  be  refracted  to  a  focus 
at  the  centre  of  the  curve  of  which  the  convex 
side  is  a  segment,  or  to  a  point  equidistant  on 
the  opposite  side.  This  plano-convex  lens  is  a 
very  common  form  of  condensing  lens  for  the 
magic  lantern  and  for  other  uses  (Fig.  7). 

If  we  have  both  surfaces  of  the  lens  convex 
(Fig.  8),  the  result  is  precisely  the  same  so  far 
as  focalizing  the  rays  to  a  centre;  only  the  dis- 
tance of  the  focal  spot  is  only  one-half  that  of 


SOLAR   HEAT 


ITS   PRACTICAL   APPLICATIONS       115 


FIGURE    7 


n6  SOLAR   HEAT 

the  former,  since  double  the  amount  of  bending 
is  done  in  the  lens. 

The  last  is  the  ordinary  "  burning  glass " 
form.  Extraordinary  things  have  been  done 
with  large  lenses  of  this  form.  They  are  used 
in  the  telescope,  field-glass,  opera-glass,  photo- 
graphic camera,  and  many  other  instruments. 
Manufacturers  of  such  articles  have  wrought  out 
many  problems  as  to  the  combination  of  these 
lenses  with  the  same  and  with  different  forms. 
Solar  engineers  may  profit  by  these  lessons ;  there 
is  a  very  wide  field  for  experiment  in  the  applica- 
tion of  the  lessons  of  practical  optics  to  the  art 
of  heliodynamics. 

A  fact  of  very  great  importance  to  this  art 
is  the  effect  of  "  cutting  "  lenses.  When  a  wedge 
is  so  cut  down  that  the  same  angle  is  kept  but 
the  wedge  thinned  in  some  parts ; 1  or  when  a 

1 A  pane  of  glass,  ribbed  in  such  a  way  as  to  form 
a  connected  series  of  parallel  triangular  wedges  of  the 
same  size,  has  been  invented  by  a  Mr.  Pennacook  and  sold 
to  persons  who  desired  to  throw  light  into  dark  rooms. 
Of  course  such  a  device  cannot  increase  the  light,  as  is 
sometimes  represented  by  the  ignorant;  but  the  rays  are 
all  turned  one  way,  in  the  direction  of  the  thicker  diameter 
of  the  triangles.  If  the  panes  were  made  with  the  trian- 


ITS   PRACTICAL   APPLICATIONS       117 


FIGURE   8 


n8  SOLAR   HEAT 

curvilinear  lens  is  cut  so  that  its  true  curve  is 
retained  while  the  thickness  is  reduced,  the  re- 
fraction is  not  altered.  But  a  large  reduction 
of  the  absorbing  or  retarding  power  of  the  lens 
is  made;  far  more  heat  will  be  carried  through  a 
"  cut "  lens  than  the  original  from  which  it  was 
reduced.  Each  of  the  foregoing  forms  is  shown 
in  its  cut  condition  above.  A  familiar  example  of 
this  may  be  seen  in  the  lanterns  used  at  switches 
and  other  points  about  a  railroad  station.  Now 
it  is  entirely  practicable  to  make  very  wide  lenses 
for  the  concentrating  of  solar  heat  by  cutting 
them.  Of  course  this  is  to  be  done  in  the  orig- 
inal plan,  not  after  the  full-thickness  article  has 
been  cast  or  rolled.  A  circular  cut  lens  may  be 
made  in  sections,  like  panes  of  glass,  all  corre- 
sponding to  the  single  plan. 

If  one  would  know  how  magnificent  results 
can  be  attained  by  this  means,  let  him  examine 
the  glasses  of  a  lighthouse  lantern.  Each  pane 
or  block  of  glass  is  a  part  of  a  lens  system; 

gular  wedges  of  different  depth,  steadily  increasing  from 
one  side  to  the  other,  there  would  be  a  concentration  of 
the  masses  on  one  band  or  space. 


ITS   PRACTICAL  APPLICATIONS       119 

through  all,  as  one,  the  rays  of  the  lamp  within 
are  thrown  out  in  a  sheet  of  light  above  the  sur- 
face of  the  sea,  for  the  mariner's  convenience 
and  safety.  By  day,  the  glasses  are  covered  with 
a  curtain;  because  the  sun's  rays,  striking  on 
them,  would  be  concentrated  upon  the  lamp  and 
set  it  afire,  to  the  great  injury  of  its  form  and 
contents.  The  cost  of  these  lighthouse  lens- 
systems  is  very  large,  for  all  lamps  are  feeble 
compared  with  the  illumination  desired  from 
them,  so  that  the  manufacturer  has  to  secure  a 
very  high  degree  of  accuracy  in  his  refractors. 
The  maker  of  refractors  for  solar  heat  will  have 
so  generous  a  supply  of  heat  to  draw  from  that 
he  need  not  attain  to  anything  like  the  same 
degree  of  nicety,  though  following  some  of  the 
same  rules  and  lessons.  And  it  will  be  found, 
after  a  strong  demand  has  developed,  that  glass 
men  will  overcome  the  conservatism  which  has 
led  them  to  decline  applications,  hitherto,  in  many 
instances.1  Lenses  have  many  advantages.  They 

*It  must  be  said  right  here  that  glass  manufacturers 
are  very  slow  to  enter  on  new  work;  and  they  have  stood 
aloof  from  the  task  of  making  lenses  suitable  for  the 
concentrating  of  solar  heat.  The  writer  applied  some  years 


120  SOLAR   HEAT 

give  a  larger  percentage  of  the  heat  that  falls 
on  them  than  reflectors  of  the  same  relative  de- 
gree of  exactness.  They  require  less  continual 
care;  if  made  in  sections  (panes)  they  may  be 
put  up  and  repaired  by  less  skilled  workmen. 
Their  surface  is  not  in  the  same  danger  of  cor- 
rosion or  abrasion  as  soft  metal,  like  silver.  For 
these  and  other  reasons  many  will  prefer  them. 
Those  who  advocate  the  superiority  of  reflec- 
tors over  lenses  for  solar  heat  concentration  may 
well  consider  the  fact  that  we  use  lenses  for  our 
sight  in  eye-glasses,  microscopes,  and  telescopes 
to  secure  the  most  perfect  concentration  of  light; 

ago  to  Alvan  Clarke  &  Sons,  of  Cambridge,  Mass.,  to  pro- 
duce what  he  desired  at  one  stage  of  his  experiments; 
they  responded  that  they  were  already  more  than  full  of 
orders  in  their  special,  astronomical  line,  and  referred  him 
to  some  French  manufacturers.  He  then  applied  to  the 
well-known  house  of  Darlot,  celebrated  for  the  production 
of  photographic  lenses,  etc.  Mr.  Darlot  responded  that 
he  had  already  undertaken  a  similar  commission  for  a 
French  physicist ;  had  spent  "  some  hundreds  of  francs  " 
in  experiments  in  the  matter,  and  found  it  impracticable. 
At  the  Columbian  Exposition  the  agent  of  a  distinguished 
French  manufacturer  of  lighthouse  lenses  was  approached 
on  the  same  errand ;  standing  beside  the  firm's  magnificent 
display  of  lanterns  of  the  largest  size,  we  asked  him  if 


ITS   PRACTICAL   APPLICATIONS       121 

why  should  we  not  do  the  same  for  the  concen- 
tration of  heat  ? 

(D)      THE    APPLICATION    OF    SOLAR    HEAT. 

All  that  can  be  done  with  heat  derived  from 
combustion  can  be  done  with  solar  heat.  The 
reader  who  has  carefully  read  the  reports  of  his- 
torical experiments  must  have  noticed  how  wide 
is  their  range.  The  cook  fills  her  stove  with 
wood  or  coal  to  get  heat  or  cooking  bread,  meat, 
fish,  fruit,  confections;  she  may  open  her  solar 
oven  to  the  sunshine,  and  have  as  much  and  as 
steady  heat  many  of  the  days,  in  the  lands  where 

it  would  not  be  an  easy  task  for  such  a  house  to  construct 
"cut-lenses"  of  suitable  character  for  heat  concentration; 
after  careful  reflection  he  answered  that  he  did  not  think 
the  firm  would  be  willing  to  undertake  the  work  on  account 
of  the  high  cost  involved  and  the  narrow  margin  for 
profit. 

The  very  large  profits  of  the  lighthouse  lens  manufac- 
ture from  the  government's  liberal  appropriations  have 
spoiled  those  men  for  the  plain,  practical  business  which 
opens  before  the  maker  of  solar-heat  lenses.  But  the 
writer  believes  that  the  task  presents  no  real  difficulties; 
and  is  confident  that  there  will  be  manufacturers  yet  found, 
of  sufficient  progressiveness  and  ingenuity,  to  take  this  task 
in  hand  and  make  successful  results  for  themselves  as  well 
as  for  the  public. 


122  SOLAR   HEAT 

sunshine  has  sway.  The  manufacturer  of  wooden 
or  metallic  goods  consumes  costly  stores  of  car- 
bon, and  handles  great  quantities  of  ashes,  in  his 
attempt  to  get  heat  for  sawing,  planing,  forging, 
drying,  bending,  cutting,  and  every  way  working 
his  materials;  his  steam  or  hot-air  engine  de- 
pends on  this  hard-sought  and  dear-bought  ca- 
loric; but  the  rays  of  the  sun  offer  him  as  high 
degree  of  temperature  when  they  are  condensed 
and  combined  suitably.  The  miner  finds  on  the 
surface  or  beneath  it  masses  of  rock  which  con- 
tain fortunes;  he  wants  power  to  hoist,  trans- 
port, separate,  melt,  and  refine  his  ores;  all  this 
can  be  done  by  solar  heat  properly  received,  con- 
centrated and  converted  into  kinetic  and  caloric 
of  the  degree  he  desires.  The  farmer  is  in  need 
of  stationary  engines  to  thresh,  husk,  and  grind ; 
of  locomotives  to  plough,  harrow,  sow,  reap, 
mow,  pile,  draw,  to  connect  him  and  his  work 
with  the  marts  of  the  world.  The  grain-grower 
and  the  orchardist  and  horticulturist  join  him 
in  asking  for  water-raising  apparatus;  and  the 
Auteuil  machine  and  the  Pasadena  engine  are  his 
reply.  Pure  country  power  may  be  had  as  well 


ITS   PRACTICAL   APPLICATIONS       123 

as  "  pure  country  milk ;  "  and  the  costless  engine 
may  replace  the  expensive  ones  now  enjoyed  by 
but  a  small  part  of  the  people  who  need  them. 

ELECTRIC    STORAGE    OF    SOLAR    HEAT. 

The  most  significant  fact  bearing  upon  solar 
heat  utilization  to-day  is  the  development  of 
electric  storage.  With  this  feature,  the  art  takes 
on  mighty  strength.  By  the  aid  of  storage  bat- 
teries, mines  may  be  lighted  throughout  the  day 
and  night;  distant  cities  may  be  illumined  from 
some  "  lone,  sequestered  vale,"  where  sunshine 
bestows  its  noiseless  benison.  Great  reservoirs 
of  water  may  be  pumped  full  in  hot  days,  and 
drawn  from  for  long  days  afterward. 

By  this  means  a  hundred  stations  may  be  com- 
bined in  one  grand  dynamic  unit.  It  may  be 
that  a  larger  concentration  of  heat  and  energy 
for  any  purpose  can  be  secured  from  solar  ap- 
paratus than  from  any  other  source  of  which 
we  now  know.  Given  a  single  "  section  "  of  land 
in  a  favored  locality,  cover  its  640  acres  for  half 
their  extent  with  furnaces  and  motors,  leaving 
the  remainder  for  roads,  cabins,  repair-shops, 


i24  SOLAR   HEAT 

storage-sheds,  etc. ;  stretch  wires  from  side  to 
side,  in  air  or  underground,  as  may  be  cheapest; 
bring  all  their  currents  to  one  spot  near  the  rail- 
road, where  materials  for  heating,  refining,  man- 
ufacturing, or  what  not  shall  be  accumulated ;  and 
the  great  manufacturing  centres  of  the  whole 
world  will  be  outdone.  Add  section  to  section, 
if  you  please;  Niagara  itself  cannot  be  stronger 
than  the  gathered  power  of  a  Nevada  ranch  or 
an  Arizona  claim.  If  one,  why  not  many  such 
gigantic  plants,  ranging  along  the  lines  of  our 
transcontinental  railroads,  inviting,  not  simply 
manufacturers  already  at  work  in  other  (coal  or 
gas  burning)  places,  but  new  companies,  formed 
to  grapple  with  some  of  those  cyclopean  enter- 
prises which  have  been  dreams  thus  far  in  human 
history,  but  may  be  realized  through  the  vast 
reach  of  this  gratuitous  force.  Trains  of  cars 
can  be  hauled  by  trolley  or  storage-battery  meth- 
ods ;  city  carting,  sprinkling,  sweeping,  and  other 
public  work  may  be  done  by  this  means;  any 
public  or  private  operations  are  feasible  by  its 
aid. 

One  of  the  most  valuable  pieces  of  work  to  be 


ITS   PRACTICAL  APPLICATIONS       125 

performed  by  heliothermic  means  is  the  manu- 
facture of  ice.  Towns  which  lie  on  the  coast 
are  now  furnished  with  natural  ice  at  low  cost; 
but  interior  towns  have  to  meet  burdensome 
freight  charges  for  the  article  from  its  northern 
sources,  or  else  pay  prohibitive  rates  for  the 
manufactured  article.  With  sun  heat,  the  farmer 
may  have  his  own  ice-house  and  cold-storage 
room,  where  he  will  hold  his  reserves  of  butter, 
eggs,  poultry,  fruit,  vegetables,  and  other  pro- 
ductions till  convenient  time  for  shipment  and 
prospects  of  favorable  prices  come  around. 

Ice  will  enter  into  the  very  process  of  his 
machinery,  too,  as  in  the  use  of  hot-air  engines; 
for  the  contrast  between  the  temperature  of  the 
sun  and  that  of  ice,  kept  in  the  shadow  under 
the  concentrating  apparatus,  will  be  great  enough 
to  give  a  capital  basis  for  the  cycles  of  compres- 
sion and  expansion  necessary  in  the  hot-air  en- 
gine. 

The  world  does  not  yet  know  how  to  make 
the  electric  current  spring  directly  from  sub- 
stances simply  heated;  but  there  may  soon  be 
an  unfolding  of  this  scheme  in  season  to  create 


126  SOLAR   HEAT 

a  nascent  electric  current  from  some  substance 
by  means  of  solar  heat. 

Droughts,  produced  by  excess  of  sunshine,  as 
the  world  has  hitherto  viewed  the  matter,  may 
now  be  overcome  by  that  very  means,  since  water 
for  irrigation  and  domestic  use  lies  at  no  consid- 
erable depth  in  great  sections  of  the  country 
whose  surface  is  habitually  parched;  and  the 
heat  of  the  sun  is  available  where  most  needed 
in  this  as  in  many  other  respects.  Famine  will 
leave  India  when  solar  engines  enter  and  possess 
the  land. 

Solar  heat  is  not  different  from  other  heat; 
it  may  be  used,  as  has  been  observed,  in  connec- 
tion with  any  apparatus  which  could  employ  the 
heat  of  burning  wood  or  coal  or  oil  or  gas.  As 
in  those  cases,  there  must  be  a  way  for  the  fuel 
—  that  is  the  sunbeams  —  to  enter  the  heat  re- 
ceptacle, and  this  door  must  be  always  open ; 
this  fire  can  be  "  banked  "  by  curtains.  Clouds 
will  diminish  the  amount  of  caloric,  and  no  stir- 
ring or  increased  draft  will  then  help  the  fireman ; 
devices  must  be  employed  to  adapt  the  machinery 
or  other  applications  to  this  variability  of  the 


ITS   PRACTICAL  APPLICATIONS       127 

heat,  in  certain  cases,  but  not  in  all.  Some  proc- 
esses will  merely  be  faster  or  slower,  as  the  sky 
is  clear  or  obscured;  and  the  caretaker  must 
test  the  work  being  done  from  time  to  time,  as 
a  cook  watches  the  contents  of  her  oven,  or  as 
stationary  and  locomotive  engineers  watch  fire 
and  "load." 

Hot-air  engines  ought  to  be  a  favorite  method 
of  applying  solar  heat  because  of  the  absolute 
inexpensiveness  of  the  material;  because  air  is 
everywhere,  while  water,  for  steam-making,  will 
be  hard  to  get,  or  absolutely  unprocurable  in 
some  spots  where  sunshine  is  abundant.  Erics- 
son approved  of  this  type  of  engine  for  the  pur- 
pose most  heartily.  The* form  of  the  engine  is 
not  within  our  province  to  discuss.  Treatises 
on  mechanics  will  inform  an  inquirer;  a  gen- 
uine mechanical  engineer  must  take  up  the  prob- 
lem in  any  given  case  where  large  interests  are 
involved. 

Steam  engines  have  been  the  principal  method 
of  utilization  with  Mouchot  and  other  distin- 
guished inventors.  The  reason  may  be  that  the 
steam-engine  has  had  wonderful  development  in 


128  SOLAR    HEAT 

its  three-quarters  of  a  century,  and  is  well  in 
hand  in  economies  and  conveniencies ;  because, 
too,  the  enormous  difference  between  one  pint 
of  water  and  1,700  pints  of  vapor  makes  a  tre- 
mendous force.  Where  water  is  easily  obtain- 
able, the  steam-engine  is  to-day  the  most  available, 
probably,  for  the  development  of  power  from 
sunbeams. 

Ammonia  gas  has  great  advantage  in  its  low 
evaporating  point;  the  Auteuil  pumping-plant  is 
an  illustration  of  the  manner  in  which  this  may 
be  used;  this  will  be  a  resort  of  not  a  few  per- 
sons for  certain  uses.  Other  substances  which 
vaporize  at  low  temperature  will  come  into  use 
of  like  quality,  wherever  the  requirement  is  for 
inexpensive  works,  and  where  these  easy  evap- 
orators are  cheap  and  abundant. 

When  once  we  have  gathered  our  heat  rays 
in  masses  or  in  focalized  intensity,  the  problems 
of  practical  application  are  not  at  all  different 
from  those  which  confront  a  man  who  has  a  fire 
of  wood,  coal,  oil,  or  gas.  Here  is  the  fire;  do 
with  it  what  you  like. 

Any  machinery  requires  human  oversight;    a 


ITS   PRACTICAL   APPLICATIONS       129 

solar  bakery  for  a  private  house  will  have  to  be 
watched  by  the  housewife  or  servant,  as  a  coal 
or  wood  or  oil  stove  would  need  to  be;  a  dozen 
great  furnaces  with  motors  attached  may  all  be 
attended  by  a  single  person.  It  seems  probable 
that  this  work  may  be  done  by  persons  not  the 
strongest  or  most  athletic;  men  and  women  who 
have  too  little  strength  or  health  to  bear  common 
burdens  of  toil  may  be  able  to  give  the  prudent 
care  and  trustworthy  attention  which  will  be 
called  for  in  the  running  of  solar  apparatus.  Of 
course  extensive  plants,  connected  with  great 
manufactories,  would  have  to  be  cared  for  by 
skilled  mechanics  and  engineers. 


CHAPTER    III. 

LOCALITIES    WHERE    SOLAR    HEAT    MAY    BE    OF 
DOMESTIC  AND  INDUSTRIAL  VALUE. 

IN  general,  any  spot  where  the  sun  shines  is  a 
place  for  gathering  and  using  its  beams  of  heat. 
For  an  hour  or  a  day  or  a  small  number  of 
days  one  can  utilize  this  force  anywhere.  There 
is  an  undoubted  field  for  the  utilization  of  solar 
heat  anywhere  wherever  the  sun  shines.  But 
the  object  of  the  present  work  is  to  point  out 
the  localities  where  solar  heat  may  be  made  a 
valuable  addition  to  the  forces  which  enrich  a 
people  and  build  up  business  enterprises. 

The  ideal  place  for  a  solar  heat  plant  would 
be  one  of  those  spots  in  South  America  where, 
if  we  may  believe  popular  reports,  no  rain  ever 
falls  and  no  clouds  linger  in  any  day.  Perhaps 
there  are  such  regions  in  fact.  More  likely  there 
130 


ITS   PRACTICAL   APPLICATIONS       131 

are  none  in  which  all  possible  sunshine  is  afforded 
through  all  the  days  of  the  year.  But  there  are 
many  thousand  square  miles  of  territory  in  both 
Americas  and  in  Asia,  Africa,  and  Australia 
where  the  rainy  days  are  very  few,  clouds  rare, 
and  the  great  majority  of  the  hours  of  possible 
sunshine  afford  clear  shining.  Eminent  examples 
of  this  class  are  Yuma,  Arizona,  with  301  days  of 
unobstructed  sunshine,  52  days  partly  cloudy,  12 
cloudy,  and  only  7  days  of  rain  in  the  round  year ; 
and  Independence,  California,  with  a  record  of 
284  clear  days,  72  partly  cloudy,  and  but  9  days 
when  a  solar  apparatus  would  be  of  no  use.  It 
has  been  demonstrated  that  the  heat  of  the  sun 
penetrates  haze  and  thin  clouds,  which  would  be 
called  "  partly  cloudy  "  condition ;  and  the  rain 
is  concentrated  into  sufficiently  short  periods  so 
that  interruptions  of  the  working  of  the  appa- 
ratus would  usually  be  short. 

The  long,  dry  summers  of  the  western  sections 
of  the  United  States  are  admirable  times  for  the 
running  of  the  plants  we  are  advocating;  and 
even  in  winter  there  are  often  periods  of  five 
or  six  weeks  at  a  time  when  the  days  are  rain- 


132  SOLAR   HEAT 

less,  so  that  the  working  of  the  furnaces  and 
motors  could  continue  with  but  brief  intervals. 

Let  us  see  what  the  extent  of  our  own  hello- 
thermic  area  is.  After  one  has  crossed  the  great 
River  Mississippi  and  the  main  trunk  of  its 
grand  tributary,  the  Missouri,  there  begins  a 
vast  region  of  prevalent  sunshine.  The  pastures 
where  cattle  in  innumerable  herds  feed;  the 
stretches  of  wheat  and  corn  land;  the  ridings 
where  buffalo  but  yesterday  roamed,  pursued  by 
red-skinned  hunters ;  the  downs  over  which  pro's- 
pectors  have  sought  not  vainly  for  signs  of  gold 
and  silver;  the  lands  which  give  track  for  rail- 
roads, along  which  the  traveller  seeks  in  vain 
for  a  shrub  as  high  as  a  man,  till  he  reaches  one 
plainly  called  "  the  Thousand  Mile  Tree;  "  those 
quiet  valleys  in  Utah,  where  Joseph  Smith's  fol- 
lowers found  refuge ;  the  "  plains,"  over  which 
thousands  of  miners  passed  in  the  fifties,  lured 
by  pictures  of  Eldorado,  the  alkali  plains  on 
which  hundreds  left  their  bleaching  bones;  the 
slopes  of  the  mighty  Nevada  chain  and  the  Coast 
and  Contra  Costa  Ranges,  and  the  wide  sweep 
of  fertile  land  in  the  valleys  of  the  Sacramento 


ITS   PRACTICAL   APPLICATIONS       133 

and  San  Joaquin  systems;  the  borders  of  the 
Golden  Gate  and  its  inland  seas;  the  rich  lands 
of  Southern  California,  where  Pacific  breezes 
modify  semi-tropical  heat  for  the  resident;  the 
great  majority  of  the  land  that  is  contained  in 
and  borders  on  these  regions  is  the  destined  home 
of  the  solar  engine. 

Note  well,  however,  that  this  broad  scope  of 
country  is  not  homogeneous.  Among  these  dry 
places  one  finds  some  very  moist  spots.  Moun- 
tains which  force  clouds  upward  on  the  wind- 
ward side  allow  their  moisture  to  fall  on  the  lee- 
ward slope.  Not  far  away  from  a  place  of  eighty 
per  cent,  of  possible  sunshine,  you  may  come  to 
a  region  of  but  half  the  year  clear.  And  years 
vary  exceedingly,  too;  which  makes  the  figures 
of  a  particular  year  sometimes  really  deceptive 
as  to  the  average  conditions.  The  admirable 
work  now  being  done  under  direction  of  our 
National  Weather  Bureau  will  give  us  a  series 
of  tables  soon,  whose  averages  may  afford  trust- 
worthy data  for  coming  students.  The  govern- 
ment ought  to  consider  this  subject  worthy  of 
special  and  expert  investigation,  since  the  re- 


134  SOLAR   HEAT 

sources  of  our  domain  are  capable  of  being  devel- 
oped more  economically  and  extensively  through 
this  channel  than  through  any  other.  But  enough 
is  known  to-day  to  authorize  the  statement  that, 
what  used  to  be  vaguely  called  "  The  Great 
American  Desert,"  with  its  borders  extending 
into  Montana  in  the  north  and  Oklahoma  in  the 
south,  stretching  over  Wyoming,  Colorado,  New 
Mexico,  Idaho,  Utah,  Nevada,  Arizona,  portions 
of  Eastern  Washington  and  Oregon,  and  the 
principal  part  of  California,  —  in  short,  what 
our  schoolchildren  are  now  taught  to  call  the 
"  Western  Highland  States,"  are  generally 
adapted  to  the  use  of  solar-heating  apparatus. 
The  following  tables,  consisting  of  extracts 
from  reports  of  the  United  States  Weather  Bu- 
reau, give  figures  of  sunshine  and  shade  for  some 
places  for  certain  years,  which  are  instructive. 
They  vary,  partly  from  the  difference  of  suc- 
cessive years,  partly,  it  may  be,  from  defective 
observation  in  some  cases.  But  they  attest  the 
great  possibilities  of  solar  heat  as  an  element  for 
the  enrichment  and  development  of  our  Western 
country. 


ITS   PRACTICAL  APPLICATIONS       135 
SOME   STATISTICS   OF   SUNSHINE. 


PLACES 

1899 

1900 

1901 

| 

u 

Partly  Cloudy 

>> 

rt 

JB 

- 

Partly  Cloudy 

>, 

1 
u 

Partly  Cloudy 

>. 

'O 

0 

Belmont,  Nev. 

194 

46 

9- 

Carlin        

166 

T59 

Carson  City      .... 
Cheyenne,  Wy. 
Crane's  Ranch,  Nev. 

155 
"3 

118 
144 

& 

192 

227 

I25 

57 

48 
81 

203 
209 

115 
40 

47 
85 

Denver,  Col  

205 

109 

51 

Elko,  Nev  

198 

127 

40 

218 

144 

3 

Fenelon     

181 

37 

M7 

189 

15 

I3l 

Fresno,  Cal  

226 

56 

83 

Golconda,  Nev. 

211 

77 

77 

216 

77 

72 

Hot  Springs      .... 

203 

38 

124 

Humboldt          .... 

229 

40 

96 

252 

16 

97 

Independence,  Cal. 

284 

72 

9 

Las  Vegas,  Nev. 

J93 

66 

14 

Lewer's  Ranch 

182 

122 

3° 

178 

149 

38 

Lovelock            .... 

208 

58 

99 

240 

ii 

114 

Martin's  Ranch 

263 

37 

65 

227 

24 

47 

Miles  City,  Mont.      . 

158 

T35 

72 

Mt.  Tamalpais,  Cal. 

196 

80 

89 

Oklahoma,  Okl. 

212 

72 

81 

Owyhee,  Nev. 

206 

82 

77 

!93 

84 

88 

Palisade             .... 

230 

J35 

197 

7 

161 

Palmetto            .... 

230 

7i 

64 

224 

76 

65 

Phoenix,  Ariz  

245 

86 

34 

Red  Bluff,  Cal.          ... 

219 

74 

72 

Reno,  Nev.        .         .         . 

162 

107 

65 

178 

103 

84 

Sacramento,  Cal. 

2OI 

76 

88 

Salt  Lake,  Utah 

15° 

1  20 

95 

San  Diego,  Cal. 

280 

40 

45 

San  Luis  Obispo,  Cal. 

208 

95 

62 

San  Francisco,  Cal.  . 

I85 

104 

76 

Santa  Fe,  New  Mexico     . 

234 

90 

32 

Wads  worth,  Nev.      . 

232 

35 

67 

Yuma,  Ariz  

3OI 

52 

12 

SOLAR   HEAT 


PERCENTAGE   OF   POSSIBLE   SUNSHINE. 


PLACES 

1898 

i899 

Boston,  Mass. 

52 

59 

Cheyenne,  Wy. 

69 

65 

Chicago,  111. 

53 

53 

Columbus,  O. 

61 

53 

Denver,  Col. 

71 

75 

Eureka,  Cal. 

45 

46 

Fresno,  Cal. 

81 

75 

Los  Angeles,  Cal. 

76 

74 

New  York,  N.  Y. 

52 

60 

Mt.  Tamalpais,  Cal. 

73 

Oklahoma,  Okl. 

73 

72 

Phcenix,  Ariz. 

84 

85 

Philadelphia,  Pa. 

58 

65 

San  Diego,  Cal. 

73 

72 

San  Francisco,  Cal. 

69 

Santa  Fe,  N.  M. 
Yankton,  S.  Dak. 

i 

80 
64 

Manufacturing  establishments  have  always 
been  located  where  the  power  lay  at  hand.  Ban- 
gor,  Me.,  Berlin,  N.  H.,  and  such  places  drew 
to  themselves  the  great  lumber  mills;  for  they 
had  mighty  rivers  with  falls,  at  which  dams 
could  be  t)uilt  and  heads  of  water  made  potent 
for  the  sawing  of  tree-trunks  into  all  sorts  of 
what  our  English  cousins  call  "  converted  tim- 
ber." Lowell,  Lawrence,  Holyoke,  and  other 
places  similarly  furnished,  attracted  men  who 


ITS   PRACTICAL   APPLICATIONS       137 

wished  to  change  the  down  of  cotton  into  mus- 
lins and  print-cloths,  or  twine  and  warp;  paper- 
making,  chair  construction,  machine  manufac- 
ture, —  all  these  and  many  more  industries  were 
first  established  by  river  sides,  where  direct  or 
indirect  currents  of  water  might  furnish  the 
power  to  aid  man's  skill.  After  a  time,  it  was 
found  that  the  irregularity  of  water-supply  was 
a  menace  to  the  constancy  of  business;  cheap 
coal  tempted  the  operators  to  put  in  steam-en- 
gines as  auxiliaries,  and  then  to  use  them  alto- 
gether; and  then  manufacturing  plants  were 
located  in  such  regions  as  furnished  cheap  coal, 
either  where  it  was  mined,  or  where  railroads 
or  shipping  most  conveniently  supply  it.  After 
natural  gas  appeared,  the  trend  was  toward  the 
seats  of  this  convenience,  until  the  recent  check 
of  this  source  of  fuel  has  stayed  the  movement. 
What  is  to  hinder  the  location  of  numerous 
manufacturing  establishments  in  our  Western 
sun-lands  when  once  the  apparatus  for  concen- 
trating and  utilizing  solar  heat  is  brought  to  a 
higher  state  of  perfection?  The  wares  which 
are  now  taken  to  California  and  Oregon,  to 


138  SOLAR   HEAT 

Nevada  and  Washington,  to  Montana  and  Idaho, 
to  New  Mexico  and  Utah,  from  Eastern  States 
and  European  empires  may  well  be  manufactured 
along  the  "Plains"  and  "Bad-lands"  and 
canons  of  "  The  Great  American  Desert."  On 
these  stretches  of  country,  where  now  the  coyote 
and  gopher  and  jack-rabbit  roam,  the  middle  of 
this  twentieth  century  may  see  a  farming  and 
manufacturing  population  of  many  millions, 
gathered  from  all  parts  of  the  world,  enriched 
and  made  happy  and  contented  by  the  very 
agency  that  has  heretofore  rendered  the  land 
desolate.  Too  much  sunshine  has  kept  vegeta- 
tion down  and  hindered  man's  activity.  Abun- 
dant sunshine,  concentrated  and  employed  by 
man,  will  give  those  plains  and  mountain  slopes 
attractions  which  will  draw  settlers  and  capital, 
and  repay  toil  most  abundantly. 

At  a  large  number  of  points  there  is  water  a 
little  way  below  the  surface,  which  may  be  easily 
pumped  up  for  irrigation  and  for  domestic  uses. 
The  great  reservoirs  now  projected  by  speculators 
and  government  officials,  to  be  constructed  at 
tremendous  expense,  will  afterward  require  a 


ITS   PRACTICAL  APPLICATIONS       139 

large  annual  outlay  for  repairs;  but  the  use  of 
sun-motors  in  pumping  water  for  each  farmer 
and  manufacturer  to  use  will  be  a  far  larger  boon 
to  the  country,  being  more  economical  and  less 
capable  of  monopoly  and  tyrannical  management. 
The  people  are  thus  interested  to  have  this  sun- 
power  developed  most  perfectly. 

The  States  which  have  been  mentioned  as 
chiefly  endowed  with  the  wealth  of  sunshine  are 
also  opulent  in  their  mineral  wealth.  Prospect- 
ors from  California  began  fifty  years  ago  to 
discover  leads  of  gold  and  silver  and  lead  in 
Nevada  and  Arizona  and  Idaho  and  Montana; 
while  equally  adventurous  prospectors  pushed 
from  Black  Hills  to  Pike's  Peak  and  into  New 
Mexico's  ancient  gulches.  All  the  way  from  the 
Mississippi  to  the  Pacific,  the  hammer  and  pick 
and  pan  and  microscope  have  done  their  work. 
And  beside  all  the  magnificent  mines  which  have 
been  developed,  there  have  been  wonderful  dis- 
coveries made  which  have  not  yet  rendered  any 
man  wealthy.  Gold  and  silver  and  copper  and 
lead  and  so  on  are  there :  proof  of  that  is  plain ; 
but  the  cost  of  carrying  coal  or  wood  for  engine 


1 40  SOLAR   HEAT 

and  boarding-house  to  the  spot  where  the  shaft 
ought  to  be  sunk,  the  cost  of  provisioning  a  crew 
of  miners  while  they  worked  the  deposits  would 
be  so  frightful,  so  far  above  what  the  mines  now 
promise,  that  bold  explorers  have  halted;  or, 
venturing  too  confidently,  have  lost  all  they  put 
into  the  venture.  Now  let  sun-motors  be  made 
at  reasonable  rates,  and  these  myriad  mines  will 
speedily  yield  their  treasures  up.  A  pair  of  men, 
armed  with  one  plant  of  this  sort,  may  do  what 
would  now  require  twenty  men;  hoisting-gear, 
haul-out-trams,  crushing-stamps,  reducing-pans, 
cooking-ovens,  electric  lights,  etc.,  will  all  be 
available  for  them. 

And  this  use  of  the  heat  of  the  sun  is  not  to 
be  limited  to  our  own  republic's  territory  by  any 
means.  Many  lands  have  large  tracts  which  have 
heretofore  passed  as  deserts  because  of  the  abun- 
dance of  the  sun's  downpouring;  this  very  fact 
is  destined  to  make  Algeria,  the  Soudan,  Egypt, 
India,  the  table-lands  of  Ecuador,  the  arid  coast 
of  Peru,  and  scores  of  other  sections  grow  opu- 
lent when  the  utilization  of  solar  heat  is  carried 
to  the  point  of  simplicity  and  economy.  >  An  in- 


ITS   PRACTICAL   APPLICATIONS       141 

describably  large  benefit  will  accrue  to  hundreds 
of  millions  of  people  by  the  subjugation  of  the 
sun  to  common  human  service.  What  a  motive 
to  the  truly  humane  inventor  and  capitalist! 

All  honor  to  the  government  of  France  for 
encouraging  Mons.  Mouchot  and  aiding  the  ap- 
plication of  his  work  in  Algeria ;  may  the  British 
and  American  governments  fall  into  line  with 
grand  force! 


CHAPTER    IV. 

GENERAL  DISCUSSION   OF  THE   SUBJECT. 

THE  use  of  the  heat  of  the  sun  has  been  within 
human  reach  all  the  years  of  humanity's  life. 
Why  has  it  become  no  more  common?  If  it  is 
as  valuable  an  auxiliary  as  this  treatise  main- 
tains, why  has  not  the  public  seen  the  fact?  If 
the  desert  may  be  made  to  blossom,  what  has 
prevented  Sahara  from  being  turned  into  one 
magnificent  oasis  ?  If  the  sun  can  furnish  a  pros- 
pector the  means  of  testing  his  discoveries  on 
the  spot,  the  miner  and  the  ranchman  a  power 
equal  to  their  needs,  why  have  the  magnificent 
capabilities  of  great  States  and  Territories  re- 
mained so  long  undeveloped? 

If  "  Vox  populi,  vox  Dei "  —  the  voice  of  the 
people,  the  voice  of  God  —  has  not  the  indif- 
141 


ITS   PRACTICAL  APPLICATIONS       143 

ference  of  the  mass  of  mankind  to  this  subject 
proven  conclusively  that  the  heat  of  the  sun  is 
of  no  substantial  value?  Why  do  not  inventors 
and  investors  enter  into  this  field  in  solid  pha- 
lanx, accompanied  by  the  rush  of  pens  and  presses 
advocating  the  cause,  and  why  are  not  common 
carriers  laden  with  freight  of  its  machinery  and 
produce?  Thus  the  doubter  carps  at  all  our  his- 
tories and  reasonings,  repeating  the  ancient  sneer : 
"  If  it  were  worth  anything,  somebody  would 
have  long  ago  found  it  out  and  made  use  of  it; 
rank  it  with  schemes  for  perpetual  motion,  with 
the  Keeley  motor  and  sea-water  gold  mines." 

To  reply  to  this  is  important,  for  such  talk 
has  frightened  away  many  men  who  had  become 
somewhat  interested  in  the  facts  of  the  case ;  and 
it  must  be  met  squarely  or  it  will  continue  to 
hinder  the  cause.  When  the  writer  asserted, 
twenty  years  ago,  in  "  Solar  Enginery,"  that 
"  the  use  of  sun-heat  is  to-day  exactly  where 
the  art  of  steam-enginery  was  on  that  October 
morning  when  Fulton  started  up  the  Hudson,  in 
1807,"  critics  of  the  pamphlet  scoffed.  But  the 
parallel  is  a  good  one.  Scorn  and  contempt  were 


i44  SOLAR   HEAT 

poured  on  Fulton's  head  while  he  was  making 
a  bold  trial  of  his  invention;  and  every  tempo- 
rary failure  in  his  operations  was  interpreted  as 
meaning  that  his  theories  were  chimerical;  the 
public  despised  his  "  raft  on  fire,"  and  it  took 
many  years  to  bring  the  people  generally  to  ap- 
preciate the  grand  achievement  of  the  inventor. 
Professor  Joseph  Henry  taught  his  pupils  that 
strokes  on  one  end  of  a  wire,  charged  with  elec- 
tricity, would  be  repeated  at  the  other  end  (writ- 
ing at  the  end  graphein  telos)  ;  he  explained  the 
whole  idea  and  had  an  experimental  wire 
stretched  around  the  class-room ;  but  these  things 
did  not  stir  America  or  England.  Morse  came, 
with  his  alphabet  and  registering  machine,  after 
long  years ;  then  the  public  wondered  why  the 
world  had  so  long  waited  for  the  means  of  com- 
munication which  seemed  so  natural,  so  easy. 
Telephone  theories  lay  in  the  brain  of  the  Eng- 
lish physicist,  Michael  Faraday,  and  found  ex- 
pression in  his  lectures  a  long  time  before  Gra- 
ham and  Bell  gave  form  and  substance  to  that 
teaching.  How  can  any  man  who  knows  such 
facts  say  a  word  against  the  possibility  or  the 


ITS    PRACTICAL   APPLICATIONS       145 

prospect  of  developing  new  resources  out  of  old 
treasures?  The  fact  that  the  public  has  been 
tardy  in  the  acceptance  and  appropriation  of  the 
natural  endowment  which  we  have  in  sunbeams  is 
not  the  slightest  reason  for  a  cavil  at  the  value 
of  the  heat  they  bring  or  the  practicability  of  its 
domestic  and  industrial  use  on  a  magnificent 
scale. 

Further,  the  facts  of  the  matter  are  unanswer- 
able. The  single  man,  Mouchot,  should  carry 
absolute  weight  with  any  reader;  the  individual 
work  of  Adams  is  irrefutable ;  the  strokes  of  the 
Ostrich  Farm  engine  are  audible  everywhere 
that  travellers  report  what  they  have  observed, 
and  technical  men  read  the  Scientific  American. 
Solar  heat  is  "no  dream;"  it  is:  let  no  man 
hereafter  speak  a  word  of  question. 

Adventurous  business  houses  have  already 
spent  much  energy  and  money  in  solving  prac- 
tical problems;  and  the  technical  schools  ought 
to  make  much  study  of  the  theoretical  side  of 
this  matter.  But  every-day  work  by  the  com- 
paratively rude  methods  may  be  performed  by 
untrained  hands.  A  great  amount  of  value  may 


146  SOLAR   HEAT 

be  obtained  from  this  vast  natural  endowment 
before  all  the  mechanics  and  dynamics  of  the  sub- 
ject are  wrought  out  in  a  suitable  fashion;  even 
as  steam-engines  were  a  boon  to  mankind  and 
a  source  of  great  individual  gains  long  before 
triple  expansion  and  vacuum  brakes  and  electric 
signals  were  invented,  or  schools  of  technology 
founded. 

Some  of  the  arguments  which  have  been 
brought  against  the  use  of  solar  heat  are  that  it 
will  cost  a  great  deal  to  construct  any  extensive 
machinery;  that  there  are  few  workmen  familiar 
with  the  subject,  or  trained  in  such  construction, 
to  be  found  in  the  chief  places  of  mechanical 
activity  and  trade;  the  fact  that  none  of  the 
distinguished  trade  schools  and  scientific  depart- 
ments of  colleges  have  noticed  the  subject  to  any 
worthy  extent;  such  are  some  of  the  stumbling- 
blocks  thrown  in  the  path  of  the  "  promoter  "  of 
solar  enginery. 

But  it  is  to  be  said  that  the  principal  mechan- 
ical centres  of  our  land,  Boston,  Worcester, 
Lowell,  Providence,  Buffalo,  Pittsburg,  New 
York,  Paterson,  Philadelphia,  Cleveland,  Chi- 


ITS   PRACTICAL  APPLICATIONS       147 

cago,  and  how  many  others,  are  places  of  more 
dark  days  than  sunny  ones;  that  solar  appara- 
tus would  only  be  a  mockery  in  their  streets ;  and 
that  the  colleges  and  technical  schools  are  simply 
the  followers  of  the  mechanic,  not  his  leaders. 
Besides,  the  regions  which  have  abundant  sun 
are  largely  under  the  heel  of  that  enemy  of  all 
industry  and  science,  the  mining-stock  gambling 
habit.  San  Francisco  and  Denver  could  in  a 
trice  build  up  a  gigantic,  useful  art  in  this  direc- 
tion, if  they  cared  for  such  things.  The  great 
railroad  corporations  might  multiply  the  popu- 
lation along  the  line  of  their  roads  by  developing 
this  industry,  if  they  would  show  as  much  dis- 
position to  benefit  the  country  as  to  reap  benefit 
from  its  people.  A  general  spirit  of  selfishness 
has  been  responsible  for  the  tardy  development 
of  this  art,  which  is  capable  of  actually  giving 
to  the  country,  in  a  few  years,  more  wealth  than 
all  our  mines  of  gold  and  silver  have  yet  be- 
stowed. 

Some  man  or  men  may  arise  who  will  do  for 
this  business  what  one  great  "  Captain  of  Indus- 
try "  did  for  the  bicycle ;  who  took  a  "  fad  " 


i48  SOLAR   HEAT 

and  made  it  a  business  of  prodigious  dimensions 
and  usefulness ;  spending  millions  in  advertising 
the  novel  article  and  informing  the  public  how 
to  use  and  enjoy  it;  critically  scrutinizing  every 
detail  of  construction,  to  the  end  that  safety 
might  go  to  the  purchaser  as  well  as  profit  to 
the  maker;  advocating  and  promoting  good 
roads  and  good  laws  to  help  and  guard  the  grow- 
ing business  and  pleasure;  bringing  the  public 
up  to  a  point  where  the  horseless  carriage  could 
be  comprehended  and  developed  at  its  present 
rate.  Such  a  combination  of  shrewd  business 
with  large  public  spirit  in  one  or  a  number  of 
men  will  find  a  magnificent  field  in  the  develop- 
ment of  the  solar  engine. 

To  resume  the  subject  of  cost,  a  prominent 
advantage  of  solar  furnaces  is  the  saving  of  fuel- 
cost.  Steam  plants  have  to  be  maintained  at  a 
vast  outlay  for  that  which  is  destroyed  in  their 
operations,  —  the  fuel  which  they  must  burn  to 
produce  their  energy.  By  all  means,  the  fuel 
destruction  of  this  day  ought  to  be  abridged. 
We  are  impoverishing  the  earth  by  our  fires; 
every  year  is  consuming  the  profits  of  manufac- 


ITS   PRACTICAL   APPLICATIONS       149 

turers  and  diminishing  the  resources  of  our  de- 
scendants and  successors.  But  the  sun  will  give 
as  much  to  the  children  of  those  who  become 
millionaires  by  its  use  as  to  the  children  of  the 
Indians  who  have  roamed  over  the  desert  plains. 
The  absolute  freeness  of  this  supply  is  a  point  of 
immense  importance,  is  a  lofty  argument.  This 
is  to  be,  not  alone  the  horseless,  but 

THE    COSTLESS    ENGINE. 

And  regions  which  are  now  feeding  on  the 
products  of  neighboring  or  distant  States  will 
be  able  to  feed  themselves  and  supply  others 
when  they  avail  themselves  of  the  wealth  which 
falls  in  daily  opulence  upon  their  ground. 

Increased  population  will  keep  up  the  trade 
of  the  country  at  large;  none  will  grow  poorer 
by  the  Northwest's  enrichment;  but  the  taxable 
property  of  our  republic  will  be  enlarged,  and  the 
whole  country  will  feel  a  quickening  from  the 
growth  of  a  part. 

If  a  plant  costs  a  thousand  dollars,  the  interest 
on  that  sum,  at  the  old-fashioned  legal  rate  of 


150  SOLAR   HEAT 

six  per  cent,  per  annum,  would  be  sixty  dollars 
a  year,  or  one  dollar  and  sixteen  cents  a  week. 
A  ten  thousand  dollar  plant  would  cost  but  six 
hundred  dollars  a  year  for  the  investment;  the 
simple  cost  of  care,  which  any  machinery  must 
have,  is  slight  compared  with  the  expense  of 
wages  or  fuel.  Mechanism  for  this  purpose  is 
no  more  liable  to  accidents  or  wear  and  tear  than 
any  other  kind ;  and  so  the  whole  issue  turns  on 
the  one  fact  of  the  saving  of  fuel.  Now  a  small 
steam-engine  will  consume  coal  enough  to  equal 
the  interest  on  the  cost  of  the  plant.  But  when 
the  supply  of  fuel  is  distant,  and  the  price  high, 
the  amount  saved  by  the  solar  furnace  is  still 
greater*  Wages  of  laborers  are  saved  by  ma- 
chinery to  a  large  extent ;  the  cheaper  the  power 
the  larger  the  saving  in  this  direction  as  well 
as  the  other.  The  advantage  of  retaining  land 
for  various  other  purposes,  which  would  have 
to  be  absorbed  for  the  storage  of  fuel,  is  no  slight 
item;  the  independence  of  the  man  who  needs 
no  fuel,  his  freedom  from  anxiety  about  supply 
and  transportation,  etc.,  are  also  of  much  con- 
sequence. 


ITS    PRACTICAL   APPLICATIONS       151 

WHAT    PROPORTION    OF    THE    TIME    WILL    SOLAR 
HEAT    BENEFIT    US? 

Some  persons  have  raised  what  they  consider 
a  serious  objection  to  the  use  of  solar  heat  in 
its  lack  of  perfect  uniformity;  some  hours  on 
many  days  are  too  cloudy  to  run  these  furnaces 
profitably  or  at  all;  some  days  are  wholly  or 
in  part  rainy  or  snowy,  having  no  sunshine  at 
all.  Every  night  is  debarred  from  use.  Only 
eighty  per  cent,  (they  grant)  of  possible  sun- 
light can  be  had,  and  that  means  only  forty  per 
cent,  of  the  entire  twenty-four  hours  of  time. 
Steam,  they  remind  us,  can  be  kept  in  operation 
continually  by  the  use  of  combustion  furnaces. 
And  they  ask,  would  not  the  loss  of  time  when 
the  sun  did  not  shine  be  so  great  that  helio- 
dynamic  plants  would  fail  to  pay  the  interest 
on  their  cost  by  the  slight  contribution  they  might 
make  in  domestic  or  industrial  lines?  To  this 
the  answer  may  be  made  that  a  vast  proportion 
of  the  purposes  for  which  the  solar  apparatus 
would  be  used  are  needed  only  during  the  waking 
hours  of  men  and  women;  that  the  period  of 


152  SOLAR   HEAT 

sunshine  is  longer  than  the  day  which  laborers 
are  willing  to  toil  now ;  and  that  power  to  accom- 
pany the  labor  of  workmen  and  workwomen  is 
doing  enough  in  many  cases  if  it  simply  operates 
while  they  are  actually  at  work.  Thus  the  sun's 
heat  will  serve  the  domestic  and  a  respectable 
portion  of  the  industrial  purposes  as  well  as 
steam  now  does,  which  is  regularly  "  shut  down  " 
when  the  operatives  are  ready  to  go  home  at 
the  close  of  their  day  of  toil. 

The  storage  of  power,  of  which  we  have 
treated  in  previous  pages,  furnishes  a  sufficient 
answer  to  the  question  in  the  case  of  those  opera- 
tions which  have  to  be  continued  by  second  crews 
of  laborers  after  the  sun  has  set,  and  those  pieces 
of  work  which  are  restricted  in  their  nature  to 
the  night,  such  as  street-lighting  and  the  illumi- 
nation and  power-supply  of  mines  at  night.  By 
storage  batteries  these  things  can  be  done  eco- 
nomically and  effectively. 

The  forty  per  cent,  of  possible  time  in  the 
round  twenty-four  hours,  which  may  be  alleged 
to  be  the  limit  of  the  reception  of  solar  heat,  is 
not,  therefore,  the  total  period  of  our  application 


ITS   PRACTICAL   APPLICATIONS       153 

and  employment  of  the  natural  endowment.  It 
must  be  acknowledged  that  we  have,  with  the 
capability  of  storage,  a  practically  continuous 
force.  Thus  the  heat  of  the  sun  is  a  definite 
addition  to  the  resources  of  the  world  now  em- 
ployed of  prodigious  content. 

ALWAYS    ENRICHING,     NEVER    IMPOVERISHING. 

The  sun-power  is  a  pure  gain  to  humanity. 
It  subtracts  nothing;  the  world  will  not  be  in 
the  least  impoverished  to-morrow  by  the  fullest 
use  of  "  visible  solar  heat  "  to-day.  Just  as  much 
sunshine  will  fall  on  a  region  where  intelligent, 
progressive  men  are  using  millions  of  foot-power 
and  feeding  millions  of  people  by  the  aid  of  solar 
caloric  as  on  a  spot  where  all  goes  to  waste. 
The  rays  that  come  down  on  the  miner  who 
develops  a  bonanza  by  their  assistance  will  not 
shrink  back  on  finding  that  result  produced,  — 
nor  can  monopoly  increase  the  price  of  the  fuel! 

We  must  consider  that  wood  and  oil  and  coal 
and  gas  are  steadily  consumed  by  use.  Not  only 
will  the  coming  generations  be  less  comfortably 
supplied  —  a  thing  most  of  us  care  very  little 


154  SOLAR    HEAT 

about  —  but  the  drain  to-day  may  produce  dis- 
tress in  our  own  homes  and  lay  an  embargo  on 
our  own  business  to-morrow.  The  coal  strike 
of  the  year  1902  has  given  an  appalling  lesson 
on  the  slavery  of  coal  consumers.  Contrast  with 
this  the  freedom  of  the  people  who  receive  daily 
gifts  of  fuel  from  the  Creator,  taking  all  they 
wish,  all  they  can  use,  freely. 

Every  friend  of  humanity,  then,  every  man 
who  cares  for  our  race  and  looks  benevolently 
forward  to  coming  ages,  must  feel  concerned  to 
see  this  department  of  economics  advance.  Every 
government  which  builds  for  to-morrow  ought 
to  devote  great  resources  to  the  rapid  develop- 
ment of  this  science  and  industry.  Every  prac- 
tical business  man,  who  is  looking  out  for  oppor- 
tunities for  better  investment  of  capital  and 
labor,  has  an  interest  in  the  matter.  Every  man, 
who  holds  his  soul  in  sympathy  with  the  great 
plans  and  benevolencies  of  the  cosmos,  should 
rejoice  at  the  anticipation  of  such  a  magnificent 
enlargement  of  human  business  and  happiness  as 
this  offers :  thankfulness  as  well  as  opulence  must 
thrive  at  every  advance  of  solar  enginery. 


APPENDIX 

THE  first  printed  book  upon  the  subject  of  the  present 
volume  —  and  its  only  predecessor,  so  far  as  the  writer 
can  learn  —  was  issued  from  the  press  of  Gauthier-Villars, 
55  Quai  des  Grands  Augustins,  Paris,  France,  in  the  year 
1869,  with  the  following  title :  — 

"La  Chaleur  Solaire 

Et  Ses 
Applications    Industrielles 

Par 
A.    Mouchot." 

A  second  edition  was  published  in  1879, — 

"Deuxieme  Edition 
Revue  et  considerablement  Augmented." 

It  may  be  interesting  to  our  readers  to  see  the  Table 
of  Contents  of  this  remarkable  book.  We  present  a  some- 
what liberal  translation. 

CHAPTER   FIRST. 

SUMMARY.  —  The  sun  is  a  source  of  most  intense  heat; 
experimental  proof.  —  The  function  of  the  solar  heat  on 

155 


156  APPENDIX 

the  surface  of  the  globe;  it  enters  into  the  movement  of 
life.  —  Transformation  of  heat  into  energy;  the  mechan- 
ical equivalent  of  heat.  —  Solar  heat  is  the  source  of  the 
only  natural  processes  (travaux}  that  man  has  learned,  up 
to  this  time,  to  appropriate.  —  Possibility  of  taking  pos- 
session of  solar  heat  power  directly;  advantages  which 
would  result  to  certain  countries.  —  A  new  solar  receiver; 
principles  upon  which  the  theory  is  founded;  easy  means 
and  slight  cost  of  producing  any  desired  temperature  in 
a  boiler  by  the  heat  of  the  sun.  —  Plan  of  the  work. 

CHAPTER   SECOND. 

SUMMARY.  —  Of  the  use  of  glass  among  the  Ancients. — 
Concentration  of  solar  heat  in  a  glass  flask.  —  The  Arabs 
used  glass  vases  to  perform  certain  distilling  processes 
by  the  aid  of  the  sun.  —  Experiments  of  De  Saussure 
and  of  Ducarla.  —  The  heat  of  the  sun  is  like  its  light, 
formed  of  an  infinite  number  of  rays  of  different  sorts. — 
Uncolored  panes  of  glass  behave  with  heat  rays  like 
colored  panes  with  light  rays;  experiments  leading  to 
this  conclusion.  —  Results  of  the  observations  of  Mellon! 
and  Sir  John  Herschel.  —  The  influence  of  the  nature,  sub- 
stance, source  of  heat,  etc.,  upon  its  transmission. — 
Chemical  rays  beyond  the  luminous  and  calorific  rays. 

CHAPTER    THIRD. 

SUMMARY.  —  Intensity  of  solar  heat  at  the  surface  of 
the  sun;  results  of  the  observations  of  De  Saussure,  De 
Flaugergues,  John  Herschel  and  De  Pouillet.  —  Influence 
of  the  dryness  or  moisture  of  the  air  on  atmospheric  con- 
duction of  solar  heat.  —  Intensity  of  solar  radiation  at 


APPENDIX  157 

noon,  certainly  is  the  same  in  summer  as  in  winter.  —  This 
is  very  great  at  mountain  tops  as  long  as  the  air  remains 
clear;  experiments  of  De  Saussure  on  the  subject  — 
Equatorial  regions  where  the  heat  is  excessive  are  those 
where  the  air  is  dryest  [according  to]  tests  made  by  Messrs. 
Soret,  Crova,  and  Violle.  —  Method  of  concentrating 
solar  heat  upon  a  surface  a  metre  square  in  one  minute, 
at  the  latitude  of  Paris. 


CHAPTER    FOURTH. 

SUMMARY.  —  Reflection  of  light  and  heat.  —  Properties 
of  mirrors,  spherical,  cylindrical,  and  conical.  —  Metallic 
mirrors  well  adapted  for  the  purpose  of  reflecting  heat  — 
The  reflective  power  of  a  polished  metallic  surface  depends 
upon  the  nature  of  the  heat  rays.  —  Experiments  of  Messrs. 
Laprovostaye  and  Dessains.  —  Silver  plates  reflect  solar 
heat  very  finely.  —  Metals  which  may  be  used.  —  Advan- 
tages and  disadvantages  of  glass  lenses.  —  Metallic  re- 
flectors preferable  for  ordinary  purposes. 


CHAPTER    FIFTH. 

SUMMARY.  —  History  of  burning  mirrors.  —  Euclid's 
treatise  on  Optics.  —  The  Mirrors  of  Archimedes  and  of 
Anthemius  of  Tralle.  —  Works  of  Arabians.  —  History  of 
burning  mirrors  in  the  Middle  Ages  and  the  Renaissance,  — 
Experiments  of  Magini,  Kircher,  Villette,  Duffay,  and  of 
Buffon.  —  [Their]  experiments  prove  the  superiority  of 
mirrors  over  lenses.  —  It  is  not  sufficient  to  consider  tem- 
perature alone  in  estimating  heat  values.  —  Hoesen's 
mirror.  —  Method  proposed  by  Ducarla  for  protecting  from 


158  APPENDIX 

cooling  the  articles  which  are  placed  at  the  focus  of  a 
burning  mirror. 

CHAPTER    SIXTH. 

SUMMARY.  —  A  comparison  of  the  methods  (appareils) 
of  Ducarla,  Herschel,  and  Franchot.  —  New  solar  re- 
ceiver; its  applications.  —  The  action  of  solar  heat  upon 
confined  air;  means  of  utilizing  the  pressure  which  results. 
—  Raising  water  by  means  of  the  sun;  fountains.  —  The 
boiling  of  water;  a  solar  kettle  (marmite  solaire)  the. 
cooking  of  vegetables  and  [various  sorts  of]  food ; 
solar  oven;  bread-baking;  distilling  spirits;  melting 
metals. —  The  effects  on  the  future  of  certain  countries 
which  would  follow  the  adoption  of  these  operations. 


CHAPTER    SEVENTH. 

SUMMARY.  —  History  of  mechanical  applications  of  solar 
heat  up  to  the  commencement  of  this  [nineteenth]  cen- 
tury.—  Hero's  engine.  —  The  process  of  Porta.  —  The 
solar  pump  of  Salamon  de  Caus ;  the  method  he  proposed 
for  increasing  the  intensity  of  the  heat  which  falls  upon 
us.  —  Experiments  of  [the  English  physicist]  Robert  Fludd 
and  of  Drebbel.  —  Martini's  clock.  —  Kircher  constructed 
various  solar  machines;  he  recognized  the  advantage  of 
confining  the  heated  air  in  a  glass  vessel.  —  Millet  Des- 
challes  proposed  to  heat  that  air  in  order  to  assist  plane  or 
concave  mirrors  [in  reflection].  —  Bellidor's  solar  pump. — 
De  la  Cliche  proposed  to  use  the  apparatus  of  Ducarla  to 
heat  steam-engines.  —  Oliver  Evans  [in  the  United  States 
of  America]  similarly  devoted  attention  to  mechanical 
applications  of  solar  heat. 


APPENDIX  159 

CHAPTER  EIGHTH. 

SUMMARY.  —  A  study  of  the  constant  fountain  of  Salamon 
de  Caus ;  its  faults,  and  the  method  of  correcting  them.  — 
The  solar  pump  of  M.  Deliancourt  —  A  new  solar  pump.  — 
The  machine  of  Cagniard-Latour ;  it  can  be  transformed 
into  a  solar  motor.  —  The  direct  use  of  solar  heat  in  making 
steam;  uses  of  solar  generators.  —  The  experiments 
(essais)  of  M.  Ericsson;  imperfection  of  his  receiver, 
which  is  that  of  M.  Franchot.  —  Alcohol,  ether,  ammonia, 
and  hot-air  engines. 

CHAPTER  NINTH. 

SUMMARY.  —  Great  solar  machines.  —  That  of  Meudon; 
that  of  Tours.  —  Results.  —  Report  of  my  mission  to 
Algeria.  —  The  machine  exhibited  in  the  Algerian  section  of 
the  World's  Fair  at  Paris  in  1878.  —  Things  done  and 
planned  there.  —  The  decomposition  of  water  by  means  of 
the  thermo-electric  pile.  —  Means  of  storing  solar  heat  for 
night  work.  —  Various  suggestions.  —  Conclusion.  —  Notes. 

On  the  last  page  of  the  cover  of  M.  Mouchot's  book  two 
works,  by  M.  Pifre,  ingenieur  civil,  are  announced,  viz.: 
"  Les  Recepteurs  Solaires,  Resultats  Econontiques  de  leurs 
applications  industrielles  en  Algerie,"  and  "Les  Recepteurs 
Solaires  en  Egypte,  Espagne,  Italie,  Amerique,  Indes  Ang- 
laises  et  Francoises,  etc.;  "  which  evidently  follow  out  the 
lines  laid  down  in  the  great  work  of  Mouchot. 

Mouchot  has  given,  as  this  summary  shows,  an  exceed- 
ingly minute,  detailed  account  of  the  intellectual  move- 
ment toward  the  utilization  of  solar  heat,  well  worth  the 
reading  and  study  of  a  college  professor  or  student  of  the 
subject  on  its  theoretical  side.  But  his  book,  if  translated 


160  APPENDIX 

wholly,  would  be  of  but  little  value  to  that  world  of 
practical  people  for  whom  the  present  volume  is  intended. 
However,  it  must  always  stand  as  a  magnificent  monument 
to  his  honor  and  the  -first  grand  beacon  in  the  development 
of  this  cause. 


Books   Published 
By    CHARLES     H.     POPE 

THE     ELWELL     FAMILY     IN 
AMERICA 

Robert  Elwell,  of  Dorchester  and  Gloucester,  Mass., 
and  his  descendants   for  four  generations,  with  the 
author's   line   completed.       By   the  late   Rev.   Jacob 
Thomas  Elwell. 
8vo,  pp.  30,  1899          .        .  Boards,  $0.75 

WARE  GENEALOGY 

Robert  Ware,  of  Dedham,  Mass.,  and  his  descendants, 
with  information  on  others  of  the  name.  By  the  late 
Miss  Emma  Forbes  Ware. 

8vo,  pp.  335,  1901.          .  .         Cloth,  $5.00 

MOOAR   (MOORS)    GENEALOGY 

Abraham  Mooar,  of  Andover,  Mass.,  and  his  descend- 
ants; by  Rev.  George  Mooar,  D.  D. 

8vo,  pp.  97,  1901    .  .  Cloth,  £2.00 

DANFORTH    GENEALOGY 

Nicholas,  of  Framingham,  Eng.,  and  Cambridge,  Mass., 
and  William,  of  Newbury,  Mass.,  and  descendants; 
with  English  ancestry.  Illustrated.  By  the  late 
John  Joseph  May,  Esq. 

8vo,  pp.  492,  1902.     Cloth,  $6.00  .•  half  leather,  $7.00 


BOOKS  PUBLISHED    BY   CHARLES  H.   POPE 
WORKS    OF  REV.    CHARLES  HENRY  POPE,    A.M. 

THE  DORCHESTER  POPE  FAMILY 

With  notes  of  other  families  of  the  name  in  England 

and  America. 

8vo,  pp.  340  and  additions,   1888.    Nearly  out  of 
print Cloth,  $6.00 

THE   CHENEY    GENEALOGY 

Descendants  of  William,  of  Roxbury,  and   John,  of 
Newbury,  and  English  families. 
Illustrated.     8vo,  pp.  580,  1897. 

Cloth,  $5.00  ;  half  leather,  $7.00 

THE   GOSPELS   COMBINED 

Or,  The  Life  of  Jesus  Christ  as  told  by  Matthew, 
Mark,  Luke,  and  John,  blended  into  one  continuous 
narrative ;  in  the  language  of  revised  version,  text  and 
margin;  words  of  Our  Lord  in  special  type. 

i6mo,  pp.  206.    Second  edition,  1901.     Cloth,  $0.50 

THE     PIONEERS     OF     MASSACHU- 
SETTS 

A  descriptive  list  of  those  who  settled  here,  1620-1650, 
as  described  in  public  records  and  authentic  documents 
of   the  period ;    "  the   foundation   book   of   American 
family  history."     Rapidly  passing  out  of  print. 
4to,  pp.  520,  1900,  supplement  1902,  with  fine  in- 
dexes, etc Half  leather,  $13.00 


BOOKS   PUBLISHED   BY  CHARLES  H.    POPE 

SOLAR    HEAT,    ITS    PRACTICAL 
APPLICATIONS 

By  REV.  CHARLES  HENRY  POPE,  A.  M. 
A  history  and  discussion  of  the  use  of  the  heat  of  the 
sun  in  the  home,  field,  factory,  etc.,  and  a  plea  for  its 
wide  appropriation.  First  book  on  the  subject  in  the 
English  language ;  in  popular  style ;  adapted  to  gen- 
eral reading  or  class-room  study. 

Illustrated.    I2mo,  pp.  160,  1903.        .  Cloth,  $1.00 


The  above  will  be  sent,  prepaid,  to  all  countries  of  the 
postal  union,  on  receipt  of  price  in  postal  orders,  or  checks 
payable  at  par  in  Boston ,  Mass.  Address 

CHARLES    H.   POPE,    PUBLISHER 
221  Columbus  Ave.,  Boston,  Mass.,  U.  S.  A. 


Mr.  Pope  makes  investigations  along  genealogical  and 
historical  lines  in  America  and  abroad ;  edits  and  pub- 
lishes Pedigrees,  Biographies,  Family  Histories  and  other 
works.  Correspondence  invited.  Address  as  above. 


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